Parser: Framework for parsing styles.

We want to be able to read user-defined styles. Eventually we'll be able
to figure out styles in terms of inheritance as well. The actual
cascading will happen in the docx reader.
Docx reader: work with new rStyle.

Just discards info at the moment, so at least it works the same.
Docx Style parser: Basic one now just takes a parent style.

This will make it easier to build the style map from the bottom up (to
avoid any infinite references).
Alias string and runStyle to CharStyle type.
Docx Parse: build a bottom-up style tree.

Two points here: (1) We're going bottom-up, from styles not based on
anything, to avoid circular dependencies or any other sort of
maliciousness/incompetence. And (2) each style points to its
parent. That way, we don't need the whole tree to pass a style over to
Docx.hs
Docx Reader: Introduce function for resolving dependent run styles.

We always favor an explicit positive or negative in a style in a
descendent, and only turn to the ancestor if nothing is set.

We also introduce an (empty) list of styles that are black-listed. We
won't check them. (Think underlines in hyperlinks).
Docx reader: Use style resolver.

We now no longer check against explicit styles.
Docx reader: Add "Hyperlink" to blacklisted styles.

This is the only one so far. We'll add others as they show up.
Docx reader: remove emph styles and strong styles list.

We no longer need the explicit lists since we're deriving them from the
ground up.
Docx reader: whitespace fix.
Merge pull request #1547 from jkr/styleparse

Docx reader: parsing styles