Interpret modules

 Command line interpret mode adapted for import().

    Given a filename, convert it to a normalized module name.
    Clean up some leftover code.

Review URL: https://github.com/google/traceur-compiler/pull/656

Closes #656.
wip
Resolve only names beginning with dot against referrerName

Review URL: https://github.com/google/traceur-compiler/pull/665

Closes #665.
pretty print as a param
Hard code RSVP version to 3.0.3

This is to redeuce diff noise due to different versions of RSVP on
different machines.
Trace normalizeName construction if the load fails

Review URL: https://github.com/google/traceur-compiler/pull/664

Closes #664.
Make pretty print an option of the ParseTreeWriter.

Make the tree writer take an option object containing a pretty print flag instead of hard coding to always use pretty printing.

Also, do not append a new line to the end o printing trees. We still append new lines after statements.

Review URL: https://github.com/google/traceur-compiler/pull/666

Closes #666.
Duplicate imports should be reported as errors

Fixes #648

Review URL: https://github.com/google/traceur-compiler/pull/667

Closes #667, closes #648.
Remove export symbol etc

Clean up our internal Symbols. The only one left after this is our ModuleSymbol.

Review URL: https://github.com/google/traceur-compiler/pull/668

Closes #668.
Extract --referrer prefix from package.json version.

node build/semverIncrement.js prints semver patch + 1 number and updates package.json
version and  devDependency version.
Require traceur node_module as devDependency.

Review URL: https://github.com/google/traceur-compiler/pull/669

Closes #669.
Remove loadSync from nodeLoader and webLoader

Left over cleanup from 39e76aca8fb1dc4b2e2f3361ad9b3c89e6ec5480

Review URL: https://github.com/google/traceur-compiler/pull/671

Closes #671.
Register traceur modules at 'traceur@'+<package.json version>.

Make target 'updateSemVer' will ncrement the PATCH semver field from package.json version.

Use System.getForTesting()

Review URL: https://github.com/google/traceur-compiler/pull/672

Closes #672.
Add missing devDependency, semver

TBR=johnjbarton

Review URL: https://github.com/google/traceur-compiler/pull/673

Closes #673.
Merge branch 'master' into keep-comments

Conflicts:
	bin/traceur.js
	src/outputgeneration/ParseTreeWriter.js
	src/outputgeneration/TreeWriter.js
	src/runtime/LoaderHooks.js
	test/unit/codegeneration/writer.js