code review initial commit

[kevinbarabash]

I messed up and commit the actually implementation in my first commit instead of have a placeholder commit to make a PR against.

The goal of this webpack loader is to implement the same semantics as the "plugins" option in third_party_js.py in webapp. This is accomplished by appending require statements to the module being loaded. Which modules are loaded by these new require statements is specified as a comma separate lists of paths in the loader's query parameter.

The test plan for 95c5134 is:

• npm run test

@jeresig could you have a look at that commit and let me know if you have any concerns?

[kevinbarabash]

FYI, I'm going to have to rewrite this b/c it's doing the wrong thing, see #2.