Add a simple spell checker to check every changed post on builds.

The spell checker uses enchant, and is currently very dumb and just
prints out all the words that have been misspelt, after the build
completes. No configuration, as of now.

Closes getnikola/nikola#594
Try installing enchant on travis.
Use an unreleased version of pyenchant.
Check for a word in all dictionaries for a language.
Merge branch 'master' into spell-check
split-site compatibility

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
fail to fix the tests

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
Merge pull request #43 from getnikola/spell-check

Add a simple spell checker to check every changed post on builds.