automatic mixin namespacing (for less)

[davidpfahler]

When #3 is solved, the importing of different less files can cause conflicts if mixins have the same name. The dependency tracking should be able to tell which mixin each call refers to and can then automatically namespace them, before the compiler is involved.

To Do:

• copy files that would be modified to a tmp/ folder
• surgically insert namespaces before conflicting mixins
• use the tmp/ files in the main file (given to the compiler) instead of the original ones