ENH: color scheme + add PCA

For educational reasons I've added PCA to this example with sawtooth waveform to more clearly expose the idea behind ICA and better relate this example to the PCA vs ICA example.  
Also, I've changed default colors to make the output more barrier free (red-green ...). 

Let me know what you think.

![Uploading Screenshot 2013-12-02 01.07.22.png . . .]()