Add recipe checking to travis test, fix some recipes

There were a couple of recipes with an extra paren, so I added a syntax check. There were a LOT of recipes complaining about `:features` so I just suppressed that. I also suppressed the github type vs git with github url and the `:autoloads nil` warnings since I didn't want to start testing a whole bunch of recipe changes. I only fixed the missing `:description` and syntax (except for `zotmacs` whose upstream seems to have moved).

I'm not completely sure about the warning suppressing option naming, I tried to follow gcc style (`-Wno-github`) but I think it may have come out a little cryptic.

False positives in general is a more difficult question (though we don't have to answer right now): supposing we remove the redundant `:features`, what about those recipes that actually need it? `:features-no-really-I-mean-it!`?

This is point 4 of #1691.