Added matchdep module and added details to installation instructions in README.md

The matchdep module allows you to use regex matching to load tasks.  This helps you to reduce boilerplate in the gruntfile by avoiding repeated calls to loadNpmTasks and it also reduces the hassle of adding additional grunt tasks in the future.

I added some descriptions to the installation instructions to be a bit more explicit about installing and configuring the dependencies.  No instructions were removed but some were made a little more explicit/verbose.