Generate Maven site and deploy to gh-pages

[dflemstr]

This creates a Maven site for the project and deploys it to http://spotify.github.io/completable-futures. I didn't add a lot of stuff there; maybe a next step could be to include the README in there too or something.

Maybe most importantly it makes Javadoc available at http://spotify.github.io/completable-futures/apidocs (or http://spotify.github.io/completable-futures/apidocs/com/spotify/futures/CompletableFutures.html) which makes it easier to give people links to the documentation.

I took the liberty to deploy the site from my local machine so that the links above actually work, and set up Travis so that everything should Just Work® when this is merged.

PS. I set this up for this repo in particular because I think we should have Maven sites for all of our Java projects, and this was the smallest project we have in the Spotify org that would let me field test the configuration.

[mbruggmann]

Good idea! Looks a bit weird on my phone though:

In any case, I'm fine with merging it to get us started with something.

[codecov-io]

Current coverage is 100%

Merging #42 into master will not change coverage

@@            master       #42   diff @@
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  Files            4         4          
  Lines           61        51    -10   
  Methods          0         0          
  Messages         0         0          
  Branches         3         3          
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- Hits            61        51    -10   
  Misses           0         0          
  Partials         0         0          

1. File ...pletableFutures.java (not in diff) was modified. more
   • Misses 0
   • Partials 0
   • Hits -10

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[econchick]

I see this is a static site - might I suggest you redirect http->https? we did it for the spotify.github.io site with this commit.

[dflemstr]

@econchick see https://github.com/spotify/completable-futures/pull/46