Add Inch to "Documentation"

This adds Inch, a little project of mine, to the list.

From the README:

> inch is a little bit like Code Climate, but for your inline code documentation (and not a webservice).
>
> It is a command-line utility that suggests places in your codebase where documentation can be improved.
>
> If there are no inline-docs yet, inch can tell you where to start.

What do you think?