Allow for clearing of require values through streams as per #10

[JesseFarebro]

Couldn't figure out the test coverage branch that got deducted, but here is an initial pull request. If you want any changes let me know

I was also going to write a test case for resetting the file module through a commonjs stream, you only have an AMD require being reset through the stream right now. Let me know

[coveralls]

Coverage remained the same at 100.0% when pulling 28e4da4 on JesseFarebro:clear-requires into 1ecd02d on wbyoung:master.

[wbyoung]

@JesseFarebro this looks good. Can you switch to === and squash to one commit?

I don't know what you mean by test coverage branch that got deducted, so if that was important, can you elaborate?

[JesseFarebro]

The coverage summary,

Branches: 83.33% 20/24

I've never worked with coveralls or code coverage before so I'm not sure. I've updated the pull request with your request.
Thanks :)

[coveralls]

Coverage remained the same at 100.0% when pulling e8cc0ad on JesseFarebro:clear-requires into 1ecd02d on wbyoung:master.

[wbyoung]

Thanks… not too concerned with 100% code coverage of branches at this point, but if the project grows, it might be worth the effort. v0.1.2 has been published with this change included.