io.ascii LaTeX table writer: add tablealign to latexdict

fixes #1777
update CHANGES.rst
Add `translate_units` kwarg that can delegate down to `fix`.
Fix reporting of which CUNITn element was changed by unitfix
Fix error reporting in Wcsprm.to_header
Add list of supported projections to wcs docs
Reformat entry in Changes.rst
Reformat entry in Changes.rst
Add more information about projection types
Merge pull request #1838 from hamogu/fix1777

io.ascii LaTeX table writer: add tablealign to latexdict
Remove some 'doctest-skip' markers that accidentally appeared in the output of the docs
Merge pull request #1862 from mdboom/docs/remove-doctest-skip-markers-from-output

Remove doctest-skip markers from output
Merge pull request #1861 from mdboom/wcs/add-list-of-projections

Add list of supported projections to WCS docs
Merge pull request #1854 from mdboom/wcs/fixing

Issues with WCS fixing
Fix #1867: Fix sorting of tables with unicode columns on Numpy < 1.6.2
Attempt to fix Python 3 / Numpy 1.5 tests.
Added initial CONTRIBUTING.md file
Merge pull request #1867 from mdboom/table/sort

Table sort fails for unicode fields in numpy 1.5
Implemented comments by @eteq
Modified section title as suggested by @taldcroft