grunt

I've added grunt for building and linting PEX:

- `grunt run` - lints, compiles coffescript and watches PEX directory for changes (re-lints after every file change)
- `grunt build` - automatically fixes js (whitespace), lints, compiles coffescript, and created build using requirejs

I've also linted both coffescripts, and javascripts and fixed all errors that I could find, PEX still works after all of this (well, my projects, and "basic" example run).

I know it's a huge pull request, but only big changes are adding gruntfile.js, rest is just whitespace fixes (some of them needed for current coffescript).

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I have some ideas for the feature:

1. maybe we could remove build/ directory (in gitignore), as running `grunt build` creates it automatically
2. grunt could also download newest requirejs, almond, and other libs (or maybe add them as git submodules?)