Fix bug with too aggressive Unicode escape sequences

Fixes #1308
Reorg TraceurLoader along the lines outline in es-discuss.

Loader: interface with spec functions .import(), .module().
Loader impl is InternalLoader. InternalLoader focused on dependencies.
TraceurLoader extends Loader implements normalize/locate/fetch.
InternalLoader uses Loader interface for .normalize() et al.
InternalLoader uses new LoaderCompiler,  internal API for Loader to Compiler.
(Renamed LoaderHooks -> LoaderCompiler, no longer related to es6 'hooks').
Remove obsolete InterceptOutputLoaderCompiler and repl.js.

Review URL: https://api.github.com/repos/google/traceur-compiler/issues/1302

Closes #1302.
Add support for transpiling ES6 Unicode regular expressions

https://github.com/mathiasbynens/regexpu
https://mathiasbynens.be/notes/es6-unicode-regex
Use HTTPS for the demo REPL

GitHub Pages offers HTTPS out-of-the box — there’s no reason not to use it.
Use the `files` directive in `package.json` instead of `.npmignore`

`.npmignore` is a blacklist, while `files` is a whitelist-based approach. The latter is much easier to maintain. See https://www.npmjs.org/doc/files/package.json.html#files for more info.

This patch does not affect the files that are included in the package.
Delete `codereview.settings`

It’s not needed anymore ever since Traceur moved to GitHub.
Fix issue with finally in async functions

We were not correctly going to the finally state after an await
when there were no more statement (including generated) after the
await in the try block.

This sets the finallyFallThrough state and updates the callback id
to go the finally state.

Fixes #1316
Simplify compiler code path and add support for sourceRoot.

The sourcemap sourceRoot is a common prefix like a baseURL for the
the filenames in a sourcemap. It allows the map to be more compact by
reducing the number of repeated strings.

Sorting out how to set this was hampered by the compile chain complexity
at the "write" end of the chain. Reducing functions and callbacks makes
things clearer.

Fixes #1324 and fixes #1310

Review URL: https://api.github.com/repos/google/traceur-compiler/issues/1325

Closes #1325, closes #1324, closes #1310.
0.0.61
Commit binaries for 0.0.62