Some minor things that have been piling up

[DGruenwald]

Changes:

• Rearranged some of the code into a more logical order.
• Added a .pow() operation using Math.pow(x, y). Useful for increasing or decreasing contrast.
• Added a globalSeed variable that gets incremented on each use to avoid 'seed collisions' in cases where there's less than 1ms between calls.
• Added a size-parameter to TG.Noise that increases the 'grid' of the noise (makes it more 'pixel-y').
• Added the posibility to 'initialize' a filter. Simply, code that gets run shortly before the main loop.
• Simplified TG.Posterize, since I over-engineered it a bit.
• Added the cosine interpolation method.
• Allowing to input rgb-values individually to .point()-functions for gradients on top of arrays.
• Copy some arguments for convenience, e.g. .tint(0.5) sets r, g and b.
• Removed extra indentation inside TG.Transform.
• Rename TG.Number to TG.Fill like discussed (Renaming TG.Number to TG.Constant #30).
• Reversed some 'offset'-parameters to make them more intuitive, so that a positive offset moves the texture to the right for example.
• Made TG.SinX and TG.SinY frequency relative to pixels, meaning setting frequency to, for example, 20 means the sine wave will be 20 pixels wide.
• Added a comment to every generator and parameter explaining what they do (maybe resolves Add some background on how to use this #33?).
• Some changes to the examples page including adding CodeMirror syntax-highlighting

The renaming of TG.Number, reversing offsets and making frequency relative to pixels breaks older stuff of course, but I made sure that the examples still work.

If something doesn't seem right, feel free to tell me!