Consider moving docs from gh-pages branch to ./docs directory

[bcantoni]

Currently the gh-pages branch has most (all?) of the tabcmd code in it as well. I had a clean-up PR #138 to fix that, but Jac suggested that perhaps we were planning to move away from gh-pages, so I closed that one.

I do prefer the ./docs method of GitHub Pages; it seems to make maintenance easier, especially when doc and code changes come along together. I can help with this if we decide to move.

If we decide not to move right now, I'd like to resurrect the cleanup of gh-pages.