fix docs title

As it appears to be hard to make Sphinx display a top-level
topic for backers without disrupting the docs' structure,
I've created a new entry in the TOC for the backers' list.
On one hand, it requires one more click to get to the list
of backers, but on the other hand, it should be more visible
in the first place.
add index entry
edit based on review
fix toc
Merge pull request #116 from guillermooo/edit-index

Fix title, move backers' list
Merge pull request #119 from guillermooo/edit-symbols

elaborate a bit on symbol transformations
edit install topic
Merge pull request #115 from guillermooo/edit-installation

edit install topic
WIP: edit metadata topic
Merge branch 'edit-metadata' of https://github.com/guillermooo/sublime-undocs into edit-metadata
edit metadata topic