Add derivative calculations to CatmullRomSpline

I added the calculation of the derivative of the spline. This finds the tangent of the curve at the desired point.
Made libgdx version configurable in gdx-setup
OpenAL: Close InputStream when loading Sound
Merge pull request #943 from volley-se/master

OpenAL: Close InputStream when loading Sound
Only move window within title bounds.

Modal windows capture all touchd owns.
Clean up stream handling
Merge pull request #948 from hneuer/streams

Clean up stream handling
Javadoc

closes #949
Merge branch 'origin/master'
Set skin on dialog table.
Add setX and setY to TextureAtlas.AtlasSprite so that it matches expected whitespace behavior.
Path interface now has the method derivativeAt()

Path interface now has the method derivativeAt() that calculates the tangent of the curve at the desired point.
Added derivatives, commentaries with expanded formula

Added derivative calculation to linear, quadratic and cubic curves.
Added commentary to explain the curve and derivative formulas
Added derivatives to b-spline
Merge pull request #951 from mbforbes/master

Add setX and setY to TextureAtlas.AtlasSprite so that it matches expected whitespace behavior.
TextureAtlas, fixed typo in previous commit
Merge pull request #954 from semtiko/patch-1

TextureAtlas, fixed typo in previous commit
Added derivative test to PathTest.java

made sprite to always point to the path direction, added a mode which the sprite will be zig-zagging through the path.
More barycentric methods.

Less to remember.
Merge branch 'origin/master'