Adding four OOCSS frameworks

I added four OOCSS frameworks to "frameworks" section.

I added them at the top of the "frameworks" because IMO they're much better examples of atomic design than the frameworks currently listed (which are far more restrictive and monolithic).

I sorted them by number of Github stars (descendingly).

More info about each framework is provided below.

Inuit
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* 3636 stars
* 543 forks
* written in SCSS
* Created by Harry Roberts of http://csswizardry.com/ fame
* Fully implements both OOCSS and BEM
* Focused on structural CSS
* One of the key projects driving the BEM-movement


Maxmertkit
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* 387 stars
* 67 forks
* written in SCSS
* Created by Moscovian developer Vetrenko Maxim
* Uses namespaced modifiers, with different namespaces for widgets, themes, size, component state and animation state
* Comes with a non-optional default theme
* While its flexible namespaced modifiers may look uglier than alternative strategies, this approach combines the readability of BEM with the flexibility of Cascade Framework


Cascade Framework
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* 128 stars
* 33 forks
* written in CSS, with SCSS version in development
* Created by Belgian developer John Slegers (*me*)
* Uses modifiers without namespaces
* Comes with an optional default theme
* It combines a look-and-feel inspired by Bootstrap 1 with a grid architecture inspired by Nicole Sullivan's OOCSS project and a modifier pattern inspired by Maxmertkit


Applepie
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* 109 stars
* 5 forks
* written in SCSS
* Created by the folks at http://railsware.com/
* Both semantic and non-semantic approach are supported out of the box
* Comes with a non-optional default theme
* It's one of the newest kids on the block, but it's growing in popularity fast