Support for standard library

[supercooldave]

Added support for standard library.
Default directory location, which is baked into compiler when compiler is built.
One module is placed in "prototype" library and a corresponding test has been added.

[kaeluka]

The change works for me, tests pass on OS X. Apart from the comments regarding the environment variable, I have no nag.

The comment regarding the env variable is not meant to imply it's a bad idea, btw. This may well be what we should keep doing for baking similar paths into the frontend in the future. If someone knows nicer ways, let's hear them!

[supercooldave]

The compiler binds to a directory within the git directory structure. If you have two git directories, then the compilers within those will bind to the possibly different local versions of the libraries.

To support a bit more flexibility, I'll add a flag that allows you to specify the location of the std lib.

In the future, we will put the standard lib in ~/.encore, but we first want to do some research on the best way of handling packages (or bundles, as we call them). So, if there's a masters or bachelors student looking for a project, then doing a survey of package managers would be useful.

[kaeluka]

Alright, that makes sense!