* [WIP] Implement automatic spell-check for docs
fixes#663
The only thing unclear to me so far is how the output of `make spelling`
should be checked - is there a possibility to check for a file (i.e.
`_build/spelling/output.txt`) to be empty, and report a failed build
otherwise?
* fix typo in requirements.txt
* add enchant library
* travis should report errors, order spelling wordlist
* change travis.yml to easier troubleshoot build issues
* fixed more typos, added more words
* add more words, fix more typos
* added more words
* added more words
* revert changes to .travis.yml
