New test and added animation state.

*AnimationState.java
*AnimationStateTest.java

Updated:
*Git ignore to ignore all LibGDX libs.
*MixTest.Java -- Reverted back to LWJGL
*SkeletonTest.java -- Reverted back to LWJGL

A few Idea project files where added. I left these in for easy future development with
Intellij Idea.