Update changelog for 1.3.0
Update changelog for 1.3.0

I added everything I did for the CPAN/Perl package support, and mentioned the Python 3 compatibility tweaks. I also made every bullet capitalized for the entire changelog, because the inconsistency was bugging me. :smile:

Oh, I also changed the version of the next release to 1.3.0 from 1.2.2, since it has major new features now.
ilastik/conda-build,sandhujasmine/conda-build,sandhujasmine/conda-build,ilastik/conda-build,takluyver/conda-build,takluyver/conda-build,frol/conda-build,shastings517/conda-build,rmcgibbo/conda-build,dan-blanchard/conda-build,mwcraig/conda-build,mwcraig/conda-build,shastings517/conda-build,sandhujasmine/conda-build,takluyver/conda-build,rmcgibbo/conda-build,frol/conda-build,shastings517/conda-build,mwcraig/conda-build,rmcgibbo/conda-build,dan-blanchard/conda-build,ilastik/conda-build,dan-blanchard/conda-build,frol/conda-build