Support multiple @document conditions (FIX)

Merge branch 'master' of git.nzoss.org.nz:alcinnz/stylish-haskell

Switch @document from conjunctive conditions to disjunctive conditions.

Implement @document rules (save regexp() conditions).

I've still got to select a regexp library to power it.

Add build instructions.

Add contribution instructions.

Merge branch 'master' of git.nzoss.org.nz:alcinnz/stylish-haskell

Describe how I'm treating the two major version numbers.

Add bounds to all dependencies.

Normalize the license.

I decided I care more about this code getting used than whether it's aiding proprietary software.
The latter doesn't appear to be much of a threat given all other browser engines are open source.

Rename to Haskell Stylist, old name was taken.

Implement var() via a PropertyParser decorator.

Expose hooks for implementing var().

The tricky part here is around CSS inheritance, it works naturally in the existing cascade implementation.

Resolve attr() functions.

It's defined during query, because that's when Stylish Haskell (or it's callers)
have easy access to the element being queried.

Update README.md

Update README.md

Update README.md

Resolve relative link tags for caller.

Export traversePrepopulatedStyles

Add additional hooks for callers:

* Resolve relative URLs.
* Set priority on any stylesheet implementation.
* Substitute content during XML Conduit traversal in place of computed styles.