Disable sudo, reshuffle travis tasks and introduce caching

Without sudo travis is executing build tasks using docker and waiting
time in this case is really small, usually not longer then 10 seconds.

postgresql-9.5 is installed via addons.apt.packages (without sudo)
But ports 5432 and 5433 are busy. So I had to ajust environment.py to
assign port from higher diapason.

And a few words about build tasks:
First task is used for executing unit tests for all different python versions
The second one is used for executing acceptance tests against etcd
The third one is used for executing acceptance tests against zookeeper
acceptance tests are executed with python2.7 and python3.5

In addition that I've introduced caching of python virtual environment.
It really helps to reduce time needed to install python modules.

.travis.yml

@@ -1,43 +1,65 @@
-sudo: required
+sudo: false
 language: python
+python:
+- "3.5"
 addons:
+  apt:
+    packages:
+    - postgresql-contrib-9.5
   postgresql: "9.5"
 env:
   global:
-    - BOTO_CONFIG='' ETCDVERSION=2.2.5 ZKVERSION=3.4.6
+  - ETCDVERSION=2.3.1 ZKVERSION=3.4.6
   matrix:
-    - TEST_SUITE="python setup.py test"
-    - TEST_SUITE="behave"
-python:
-  - "2.7"
-  - "3.4"
-  - "3.5"
+  - TEST_SUITE="python setup.py"
+  - DCS="etcd" TEST_SUITE="behave"
+  - DCS="exhibitor" TEST_SUITE="behave"
+cache:
+  directories:
+  - $HOME/virtualenv/python2.7.9
+  - $HOME/virtualenv/python3.4.2
+  - $HOME/virtualenv/python3.5.0
 install:
   - |
+    set -e
+
     if [[ $TEST_SUITE == "behave" ]]; then
-        sudo bash -c '
-            /etc/init.d/postgresql stop
-            apt-get -y remove --purge postgresql-9.1 postgresql-9.2 postgresql-9.3 postgresql-9.4
-            apt-get -y autoremove
-            apt-key adv --keyserver keys.gnupg.net --recv-keys 7FCC7D46ACCC4CF8
-            echo "deb http://apt.postgresql.org/pub/repos/apt/ precise-pgdg main 9.5" >> /etc/apt/sources.list.d/postgresql.list
-            apt-get update
-            apt-get -y install postgresql-9.5
-            /etc/init.d/postgresql stop'
-        curl -L https://github.com/coreos/etcd/releases/download/v${ETCDVERSION}/etcd-v${ETCDVERSION}-linux-amd64.tar.gz | tar xz -C . --strip=1 --wildcards --no-anchored etcd
-        curl -L http://www.apache.org/dist/zookeeper/zookeeper-${ZKVERSION}/zookeeper-${ZKVERSION}.tar.gz | tar xz
-        mv zookeeper-${ZKVERSION}/conf/zoo_sample.cfg zookeeper-${ZKVERSION}/conf/zoo.cfg
-        zookeeper-${ZKVERSION}/bin/zkServer.sh start
-        while true; do
-            echo -e 'HTTP/1.0 200 OK\nContent-Type: application/json\n\n{"servers":["127.0.0.1"],"port":2181}' \
-              | nc -l 8181 &> /dev/null
-        done&
+        if [[ $DCS == "etcd" ]]; then
+            curl -L https://github.com/coreos/etcd/releases/download/v${ETCDVERSION}/etcd-v${ETCDVERSION}-linux-amd64.tar.gz | tar xz -C . --strip=1 --wildcards --no-anchored etcd
+        fi
+
+        if [[ $DCS == "exhibitor" ]]; then
+            curl -L http://www.apache.org/dist/zookeeper/zookeeper-${ZKVERSION}/zookeeper-${ZKVERSION}.tar.gz | tar xz
+            mv zookeeper-${ZKVERSION}/conf/zoo_sample.cfg zookeeper-${ZKVERSION}/conf/zoo.cfg
+            zookeeper-${ZKVERSION}/bin/zkServer.sh start
+            while true; do
+                echo -e 'HTTP/1.0 200 OK\nContent-Type: application/json\n\n{"servers":["127.0.0.1"],"port":2181}' | nc -l 8181 &> /dev/null
+            done&
+        fi
     fi
-  - pip install -r requirements.txt
-  - pip install behave codacy-coverage coverage coveralls
+
+    for pv in "2.7" "3.4" "3.5"; do
+        source ~/virtualenv/python${pv}/bin/activate
+        for p in '-r requirements.txt' 'behave codacy-coverage coverage coveralls flake8 mock pytest-cov pytest'; do
+            pip install $p
+        done
+    done
 script:
-  - PATH=.:$PATH $TEST_SUITE
-  - if [[ $TEST_SUITE == "behave" ]]; then PATH=.:$PATH DCS=exhibitor $TEST_SUITE; else python setup.py flake8; fi
+  - |
+    for pv in "2.7" "3.4" "3.5"; do
+        source ~/virtualenv/python${pv}/bin/activate
+
+        if [[ $TEST_SUITE == "behave" ]]; then
+            if [[ $pv != "3.4" ]]; then
+                if ! PATH=.:$PATH $TEST_SUITE; then
+                    grep . features/output/*/*postgres?.*
+                fi
+            fi
+        else
+            $TEST_SUITE test
+            $TEST_SUITE flake8
+        fi
+    done
 after_success:
   - coveralls
-  - if [[ -f coverage.xml ]]; then python-codacy-coverage -r coverage.xml; fi
+  - if [[ $TEST_SUITE != "behave" ]]; then python-codacy-coverage -r coverage.xml; fi