Improve Travis matrix for Python #22

Signed-off-by: Philippe Ombredanne <pombredanne@nexb.com>

Author: pombredanne

.travis.yml

@@ -1,20 +1,16 @@
-# This deliberately is not "python" as a work-around to support
-# multi-os builds with custom Python versions in Travis CI.
-language: cpp
-
 os: 
   - osx
   - linux 
 
 env:
     matrix:
-        - PYTHON_EXE="`which python2`"
-        - PYTHON_EXE="`which python3.4`"
-        - PYTHON_EXE="`which python3.5`"
-        - PYTHON_EXE="`which python3.6`"
+        - PYTHON_EXE="`pyenv install -s 2.7.6 && pyenv local 2.7.6`"
+        - PYTHON_EXE="`pyenv install -s 2.7.13 && pyenv local 2.7.13`"
+        - PYTHON_EXE="`pyenv install -s 3.5.3 && pyenv local 3.5.3`"
+        - PYTHON_EXE="`pyenv install -s 3.6.1 && pyenv local 3.6.1`"
 
 install:
-    - PYTHON_EXE=$PYTHON_EXE ./configure
+    - ./configure
 
 script:
     - "bin/py.test -vvs"