Allow compiling modules to RequireJS syntax.

This adds:
  - RequireJsTransformer, which produces RequireJS syntax code,
  - src/node/to-requirejs-compiler.js, which compiles files one-by-one.

The unit tests are pretty lame, but I wanted to at least get it set up so that it's easy to add more
unit tests in the future.
Add integration tests for RequireJS.
Add make targets for running a subset of tests (unit/features/requirejs)

make test/unit
make test/features
make test/requirejs
Add Node.js API.

This API is what you get when you `require('traceur')`.
It is supposed to be used by custom Node.js scripts or tools such as Grunt or Karma.
Remove left overs from builtin module names
Implement import 'name'

`import 'name'` only fetches the module, it does not execute the module body.

Fixes #524, #453, #447
Import assert in PaserTreeValidator
Fixes #532.
Add test/self-compile.html appling bin/traceur.js to src/traceur.js
So we can use devtools on self-compilation
Merge branch 'webSelfCompile' of git://github.com/johnjbarton/traceur-compiler into johnjbarton-webSelfCompile
Fix to-requirejs-compiler.js for Windows path separators
Refactor options to allow arbitrary string values.

Use this to replace options.requireJsModules and use
options.modules = 'requirejs' instead.
Add parseStatements to PlaceholderParser

And use that in the CPS transformers.

Fixes #523

Review URL: https://github.com/google/traceur-compiler/pull/536

Closes #536, closes #523.
Convert CodeLoader() to more closely follow ES6 Loader()

Isolate reporter and project in InternalCompiler.
Rename ModuleRequireVisitor -> ModuleSpecifierVisitor

Review URL: https://github.com/google/traceur-compiler/pull/540

Closes #540.
Add 'make self' and update self-compile.html

This separates bin/traceur.js from src/node/*:
 in working on module loading use self-compile.html
 to debug compilation, then make test to deal with src/node.

Review URL: https://github.com/google/traceur-compiler/pull/541

Closes #541.