Enforce `LF` newlines

Like @XhmikosR [pointed out](https://github.com/h5bp/html5-boilerplate/pull/1617#issuecomment-58865637), there are some [newline](http://en.wikipedia.org/wiki/Newline) related problems with the current setup on Windows.
 
e.g.: When the build script is run, files from `node_modules` (that have `LF` newlines, and which won't be [normalized by `git`](http://git-scm.com/docs/gitattributes#_end_of_line_conversion)) will be copied to the `dist/` directory and it will appear to Windows users as if they where changed (+ some of the current tests will fail).

<img src="https://cloud.githubusercontent.com/assets/1223565/4612435/7af85776-52c7-11e4-84e1-4ed56c931a07.png">

To fix this, we could just force `LF` newlines and be done with it (otherwise, we could use [`require('os').EOL`](http://nodejs.org/api/os.html#os_os_eol) and ensure that, for example, when the files are copied, the newlines are the ones used by the OS, but IMHO that isn't really a good solution).

If I missed something, or there is a better way of solving this, let me know!

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Note:  This is a development related change (does not modify anything distributed to the end user).