This changes the pre-commit hook that we've used for years to keep the
version value found in `package.json` in sync with the one in
`mustache.js`, to change `mustache.mjs` instead since that's where the
source code lives now.

Previously when replacing dependency installation with `npm` rather than
`rake`, there were still install task references found in `Rakefile`
which should have been removed as well.

```
$ npm version patch
v2.3.1

...

npm ERR! > minifying `mustache.js`...
npm ERR! rake aborted!
npm ERR! Don't know how to build task 'install_uglify'
```

Those `install_*` tasks does not exist anymore, as installing those
dependencies are done with npm now.

Refs https://github.com/janl/mustache.js/pull/666

Previously mocha, uglifyjs and jshint used when publishing a new version were ensured / installed by `Rakefile` via the pre-commit git hook. Those modules were automatically installed globally if not present in `$PATH`.

Installing modules globally has one particular downside that we should avoid: we can't ensure developers publishing new mustache.js versions have the same version of these 3rd party modules installed.

If instead we make these modules local dev dependencies, we can ensure which versions are installed, and we make 3rd party dependencies explicit by listing them in `package.json`, rather than in `Rakefile`.

- Cleaner separation of responsibilities in the code between
  scanning, parsing, compiling, and rendering functions.
- Much faster

This commit is a complete rewrite of the core mustache.js file with two
main goals: 1) a major performance boost and 2) better compliance with
the mustache spec.

In order to improve performance templates are pre-compiled to JavaScript
functions. These compiled functions take a view, a partials object, and
an optional callback as arguments. They are cached to prevent
unnecessary re-compilation of an already compiled template. Both of
these enhancements facilitate a generous boost in performance.

A few other notes:

- The mustache.js file is now both browser and CommonJS ready without
  any modification.
- The API exposes two main methods: Mustache.compile and
  Mustache.render. The former is used to generate a function for a given
  template, while the latter is a higher-level function that is used to
  compile and render a template in one shot. Mustache.to_html is still
  available for backwards compatibility.
- The concept of pragmas is removed to conform more closely to the
  original mustache spec. The dot symbol still works to reference the
  current item in an array.
- The parser is much more strict about whitespace than it was before. The
  rule is simple: if a line contains only a non-variable tag (i.e. not
  {{tag}} or {{{tag}}}) and whitespace, that line is ignored in the
  output. Users may use the "space" option when compiling templates to
  preserve every whitespace character in the original template.
- The parser is able to provide detailed information about where errors
  occur when parsing and rendering templates, including the line number
  and surrounding code context.

You can now run `rake jquery` and friends without installing rspec.
Closes #135.

Use fancy regex to auto-fill the version number.
Closes #37.