Move stuff around

* Remove examples. They'll have their own git repos
* Move python scripts to //bin/
* Remove python scripts for running examples
* Move templates to //templates/
* Remove third_party stuff
Remove .gitmodules
Remove Makefile and move logic to build.ninja

Also remove example-only build logic.
Switch to CommonJS style module loading.

This will make it easier to use node packages.
Move build.ninja->common.ninja

This way other repos can use common rules/variables.
Remove promise library, change commit callback to node-style.

The promise functionality can be duplicated by using bluebird.spread, for
example. I changed commit to be node-style so bluebird.promisify can be used.
Add generated dist/ files.

Also add index.js so this library can be "required".
template/glue.js requires "2nacljs" now.
Add --define flag to easy_template.py

Lets you add key/value pair to the template dict via the commandline.
Run pnacl-compress after finalizing.
Use $root variable in common.ninja

This allows reusing common.ninja from another project:

    root = {path/to/2nacljs}
    include $root/common.ninja
Add build.ninja template for use by external projects.
Build into out/obj instead of out/2nacl/obj
Add "do not edit" warning to build.ninja template
Add -o options to easy_template.py.

Also refactor the main() function a bit.
In easy_template.py, automatically make output directory.
Factor out embed creation, to make node-based testing easier.
Remove makeModule, instead return Module directly.

This is consistent with many other JavaScript types.
Enable SDK download rules

Also, fix them so they don't download every time.
Add package.json