Support Web Worker context for polyfills
Improve source-maps=memory.

Correct the key for sourcemaps in mode 'memory'
Add unit test for sourceMaps:memory from interpreter.
Add sourceURL when the input name differs from output name.

Review URL: https://api.github.com/repos/google/traceur-compiler/issues/1534

Closes #1534.
Move ./test/runner.html -> ./testRunner.html.

When run under node, the test system assumes that we start in the root of the Traceur directory.
This assumption is baked into various paths in the tests and expected error messages. To mimic this
assumption in the browser tests we need to move the test file up on directory to the root.
Fixup Loader tests for test/ path.
This is the browser cleanup after removing the 'chdir test'.

Review URL: https://api.github.com/repos/google/traceur-compiler/issues/1555

Closes #1555.
Extends expression should be a LeftHandSideExpression

fixes #1556
0.0.79
Remove the need for inputFileExtension_

We no longer care what the file extension is since we do not append
a file extension when we resolve the module URL.

Fixes #1544
Refactor sourcemap generation to combine generator and sourceUrl.

This helps ensure the generator has the same sourceURL as the //# source.
Update SourceMap.js test.

Review URL: https://api.github.com/repos/google/traceur-compiler/issues/1561

Closes #1561.
Add Math polyfill

This implements the new ES6 Math functions.

The implementation is based on V8 and MDN as well as the spec.

The tests are mostly just smoke tests. I'm not testing a lot of
edge cases.
Write the .map file in the same directory as the output file.
Fixes #1538
respond to review