Adding ECO templates and improving Windows (OS) support.

Hi,

Recently I was working with mincer on a Windows installation of nodejs, and I find some problems with pathnames due the different path separators (`'/' != '\\'`).

I would like also to work with ECO templates, not only in conjunction with JST, but also to generate CSS files , JS files and so on. (The greatest challenge is return a function code when using with JST, otherwise evaluate this function)

This pull request tries to solve both issues, providing a better support for Windows users and add a ECO engine compatible with other processors.

The support for precompiling EJS with JST was also improved and some tests using `mocha` test framework were inccluded.