Fix outline-promote/demote space issue and add extra-face support

[jdtsmith]

This PR fixes #63, which results from an unnecessary space being added directly into outline-regexp. This space is needed for proper font-locking, so it is included there.

Also included is a new customize variable outshine-outline-extra-face, which, if set, can be used to configure the face of the outline match itself (e.g. ;;;;, # ***, etc.).

For example, by adding :overline and :extend to the outshine faces, you can then achieve some good-looking separators (see below). Along the way, outshine-headings-list is generalized.

[jdtsmith]

Here's an example of the new face configurability in use:

[alphapapa]

Apparently I overlooked this PR for a while, until it appeared in my issues list again just now. Please feel free to ping me in the future if I overlook it again (I don't work on this project very often).

I'll make some comments as a review. Thanks for your work on this.

[jdtsmith]

Apparently I overlooked this PR for a while, until it appeared in my issues list again just now. Please feel free to ping me in the future if I overlook it again (I don't work on this project very often).

Thanks no worries. I've been using this branch for several months without problem.

[alphapapa]

Thanks. As a final step, if you would update the changelog in the readme and squash the branch, it could be merged directly then.

[jdtsmith]

Thanks. As a final step, if you would update the changelog in the readme and squash the branch, it could be merged directly then.

Done thanks.

[jdtsmith]

@alphapapa: a ping, as requested.

[jdtsmith]

Closing this in favor of my new much simpler mode outli which includes this type of styling by default.