Added Grayscale and Marrakesh schemes

Addes the ####Grayscale and ####Marrakesh color schemes. 

Grayscale is a monochromatic scheme, with various tones of gray (much like the Greenscren scheme, but gray in hue).

Marrakesh has some "exotic" color combos, like golden-like yellow on dark brown and a vibrant background for the light theme. 

Both themes have adjusted lightness values for good contrast and readability between the foreground/highlight colors and the background with both the light or dark backgrounds. It was achieved converting the hex colors to CIE-L*A*B* and ajusting the L* (lightness) values before converting back to hex. All the highlight colors were chosen from regular color wheel intervals (like triadic, tetradic, split-complementary etc) instead of arbitrary selection, to guarantee a balanced palette. 

####Screenshots

Grayscale Dark 
![graydark](https://f.cloud.github.com/assets/6315043/2269758/2b2ba8ce-9ee0-11e3-9112-925490387451.png)

Grayscale Light side
![graylight](https://f.cloud.github.com/assets/6315043/2269764/47095d84-9ee0-11e3-86fb-eb4c904a7631.png)

Marrakesh Dark
![marrakeshdark](https://f.cloud.github.com/assets/6315043/2269767/4f3e78d6-9ee0-11e3-9e29-88a3cab928f0.png)

Marrakesh Light
![marrakeshlight](https://f.cloud.github.com/assets/6315043/2269773/8d9cb944-9ee0-11e3-882a-f032929d8c30.png)