Slime Icons

Adds icons for Cerulean Slimes, Pyrite Slimes, Bluespace Slimes, and
Sepia Slimes.
Merge remote-tracking branch 'upstream/master' into Slime-Fix
Missing Slime Reactions

Sepia, Cerulean, Bluespace, and Pyrite slimes now have reactions.
Merge pull request #523 from TheDZD/Slime-Fix

Invisible Slimes Sprites & Extract Functionality Fixes