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.
Added Function getRemoteAddress() for Socket so it´s possible to implement reconnection logic or peer to peer networking
Add Matrix4#setTranslation(float, float, float)
Frustum: add methods using floats instead of Vector3
Stringbuilder: add minimum length for int/long
Made libgdx version configurable in gdx-setup
Only move window within title bounds.

Modal windows capture all touchd owns.
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.
Added allowIpod to IOSApplicationConfiguration

Added a new variable to IOSAppConfig called allowIpod in order to be
able to play the game without stopping the background music from iPod
app.
Also, modified the constructor of IOSAudio to pass the
IOSApplicationConfiguration from IOSApplication.
Merge pull request #1 from libgdx/master

Update