implemented .width() and .height() methods
implemented .outerWidth() and .outerHeight() methods
use typeof to check for boolean
updated readme for width/height/outerwidth/outerheight
implemented .css() method
Fixed comments from pull/#7 (cache getComputedStyle, added TODO comments)
Merge pull request #7 from garthenweb/jquery-dimensions

implemented .width()/.height(), .outerWidth()/.outerHeight() methods