Update .travis.yml: added the installation steps for 'wxPython'
partially reverted e70992d
Update .travis.yml: fixed the patching of wxPython 2.9.4.0
Update .travis.yml: added a requirement of 'wxPython'
Update .travis.yml: added a requirement of 'wxPython'
Merge pull request #31 from glarrain/travis_wxpython

Update .travis.yml: added the installation steps for 'wxPython'