Adds spell check in Travis

[joaomcteixeira]

To my understanding the current version does not perform spell check on the CI servers. I found it very useful in my projects.

Additions:

• Added spell env to tox loop
• Added spell check run on Travis.
  • running spellcheck on Travis we can avoid running it on AppVeyor, right?
  • relates to #12

Any additional discussions welcomed :-)

[ionelmc]

So there was a reason spell ain't in the CI configuration: it's a huge hassle to get it to return exit code 0 (you usually end up with ridiculous whitelist). In practice what I do is run it once in a while locally to check that I don't do any gross typos and ignore the exit code.

[joaomcteixeira]

Hi, thanks for the quick reply. Interesting, I am using it with that configuration I proposed here. So, spell just runs in Travis and for py37 (in my case). Every time it passes in my tox locally it passes in the server, so far for this week that I have been testing it intensively. In some of my test repositories I added this last line to the conf.py file:

if os.getenv('SPELLCHECK'):
    extensions += 'sphinxcontrib.spelling',
    spelling_show_suggestions = True
    spelling_lang = 'en_US'
    # https://sphinxcontrib-spelling.readthedocs.io/en/latest/customize.html#private-dictionaries
    spelling_word_list_filename = ['spelling_wordlist.txt']  # <- this one

But in my last experiments it seems no to be necessary.

Can't add more info to the cause. Let me know your last thoughts.