Added some small methods to Circle

-Area, circumference, some new constructors, etc.
-Mostly to test the LibGDX contribution waters
Changed Rectangle's uses of Float.floatToIntBits to NumberUtil's version

-Same for Circle, too
Added area, circumference, and some miscellaneous methods to Ellipse
Changed uses of floatToIntBits to floatToRawIntBits

-Oops
More equals() and hashCode() methods
Removed a superfluous import
Merge branch 'master' of https://github.com/libgdx/libgdx
Added volume/area and perimeter/surface area methods to a few shapes
Removed NumberUtils.floatToIntBits in GridPoint2 and GridPoint3

-Oops
Merge pull request #2018 from JesseTG/master

Simple changes to the math package for convenience