Add a script that fetches glowkit PRs for travis

Also reorganize .travis.yml slightly (actual build stuff goes in the
script step, preparations go in the install step)
Clone git repo to a temporary directory
Support links in the format `GlowstoneMC/Glowkit#000`
wrapper function for curl that provides access token
PLEASE STOP SHOUTING I CAN HEAR YOU CLEARLY
loop over detected issue/pr links and ask github if they are open PRs

advanced bash programming right there

fun fact, i've contributed more bash code to this project than java code
remove some emptiness from travis
this script is now more environmentally friendly
Interpret world seed as number if possible (fixes #427).
Fetch UUIDs from Mojang if needed (fixes #227, fixes #365).

UUIDs are only fetched if online mode or proxy support is enabled.
Additionally fixes problems when player data files are missing a last
known username.
Fixed or added several broken inventories.

Added GlowInventory#getRawSlots() to handle a protocol special case.
Changed TEContainer to take an inventory rather than an inventory type.
Adds or fixes enchantment tables, anvils, brewing stands, furnaces,
workbenches, dispensers, droppers, and hoppers.
Merge branch 'master' into travis-glowkit-fetcher
get jq for PRs only