Update mat2 functions to column-major

I changed mat2.multiply, mat2.rotate, and mat2.scale to assume column-major layout for matrices passed in, and to output values in column-major layout. I also updated the mat2 jasmine tests to check values against a column-major layout. These fixes will correctly match vec2.transformMat2, which as of version 2.1.0, assumes the matrix passed in has column-major layout.


Here are the calculations if someone wants to check my work,
![image](https://f.cloud.github.com/assets/2000785/1321247/57886d72-33a5-11e3-91b9-05a9666792b6.png)