travis: Remove python version requirement

Travis recently changed how python is supported, but apparently
what we were doing never actually worked: if you specify java
as the language, the python block is ignored.  So we're stuck
with whatever the build environment for the specific java
version provides.  This patch removes python from the matrix
excludes, which should restore the matrix exclusions.
Merge pull request #849 from rleigh-dundee/travis-python

travis: Remove python version requirement
Merge pull request #847 from melissalinkert/rebased/develop/javadoc-copyright

Fix the copyright statement on generated Javadocs (rebased onto develop)
Ignore text nodes when parsing XMLAnnotation's value

This fixes an error parsing Modulo annotations
(e.g. FLIM-modulo-sample.ome.tiff) in Matlab.