Fixed grid alignment issue

Reduce size of grid, normalized it (all emotes the same size) and made
large icons scale down. Fixes #5
Added transition effect on popup hover.

Added transition for a solid contrast of the emotes.
Reverted centering from c76050983bbb3dacf9e57b654b4c04abc7b41244 as it
just didn't work out the more I tested it.
Increase check time for emote sets

Ref #3
`window.CurrentChat.user_to_emote_sets` doesn't populate right away--it
is delayed. The previous fix was to just refresh until emotes appeared,
but this only worked because `user_to_emote_sets` actually populated
quickly enough. Upped the check time to 20 seconds, but may be adjusted
in the future.
Change where emotes usability is checked

Changed to checking after we know for sure what the emote sets are.
Previously, it was checking right when the API returned the emotes, but
by then the emote sets weren't known. This will go hand-in-hand with
a05b2ba85895409e3db45a1f0ae28c9e668d3224
Fix emote usability check. Ref #3

Previously, checking usability when API call was done. As emote sets
weren't always populated at the time the API finished, sub/turbo emotes
weren't always shown.

API call will now push to `rawEmotes` and `emotes` will be the usable
ones. `checkEmotesUsable` will run every time `populateEmotes` is run.
Although it may take some time to get the proper emotes, it is now in
line with the way Twitch handles it.
Fix sub emotes color & remove let keyword

Subscription emotes don't get their color the same way they used to.
Forget to include this change while doing the other commits in #3

Also changed "let" back to "var" as Firefox is still the only browser to
support it.
Inject script into document for Chrome

This may be extended to other browsers if need be. Ref #1 and #10
Prevent script from running twice

When installing multiple instances of the script, it bugs out (multiple
buttons plus glitches). If there has already been a button placed on the
page, assume it has already been ran and exit.
Merge remote-tracking branch 'origin/dev'
Version bump + remove Chrome incompatibility