Async Functions: Fix implicit return as well as rethrowing

The async function should complete with undefined if there is no
return. It should also lead to a rejected promise if there is an
uncaught exception.

Fixes #933
WebPageTranscoder cannot pass name as argument.

(Caught by recent destructuring check.)

Review URL: https://github.com/google/traceur-compiler/pull/945

Closes #945.
Report file not found as 'File not found'

Review URL: https://github.com/google/traceur-compiler/pull/946

Closes #946.
Upgrade CodeMirror to v4

This allows multiple selections which are awesome.

Enable the sublime keymap. Based on demo at
http://codemirror.net/demo/sublime.html
Merge pull request #944 from arv/code-mirror-4

Upgrade CodeMirror to v4
0.0.34
Impl TraceurLoader.importAll, loadAsScriptAll.

importAll(array-of-names) promises array of modules.
loadAsScriptAll(array-of-names) promises array of script evaluation results.

Review URL: https://github.com/google/traceur-compiler/pull/949

Closes #949.
Update Object.assign signature. Fixes gh-954

Updates Object.assign to accept an arbitrary number of source objects whose own, enumerable property names and corresponding values are copied to the target. (Per April 9 TC39 consensus)

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
Avoid reassing module.exports on CommonJS modules

Replaced `module.exports = {...}` with `Object.defineProperties`.

Fixes #947
Report internal errors even when using Promises.

The part of traceur that uses promises is susceptiable to mystery errors.
Avoid some of this in InternalLoader.
Catch errors in inline-module loadNext() and report to console,

Review URL: https://api.github.com/repos/google/traceur-compiler/issues/952

Closes #952.
Reject invalid fetch arguments  with TypeErrors

Review URL: https://api.github.com/repos/google/traceur-compiler/issues/951

Closes #951.
Replace backslashes in test error messages, they may contain windows filenames.
Add a newline to file not found messages.
Fixes #956
Closes #957
Merge pull request #957 from johnjbarton/windows-error-mismatch

    Replace backslashes in test error messages, they may contain windows filenames.
    Add a newline to file not found messages.
    Fixes #956
    Closes #957
Update CONTRIBUTING.md
Rename initialiser to initializer

The spec changed to US spelling too.
Restructure super runtime calls a bit to reduce code

This also removes the in operator which is slow.
HoistVariableTransformer should understand destructuring
Enable console and log transcoded source for generated-code-dependencies...

When running generated-code-dependencies, the transcoded source and
the traceur-runtime are combined and executed in a new JS sandbox. The
sandbox does not contain the `console` object so console logging fails.

Add flag true to executeFileWithRuntime() in generated-code-dependencies.js
to add the console for logging.

Review URL: https://github.com/google/traceur-compiler/pull/972

Closes #972.
Fix windows paths in tests

Turns out we were normalizing the expected error. We need to
normalize the actual error.

Fixes #956
Remove unnecessary pipe operators in Makefile.

Fixes #973

Review URL: https://github.com/google/traceur-compiler/pull/976

Closes #976, closes #973.