Remove global-rainbow-delimiters-mode.
Don't propertize if the syntax table is unset

`rainbow-delimiters-mode' may be restored via desktop.el. When this
happens inside an `mmm-mode' buffer, the subregion-specific values of
the syntax table will not be restored, and so
`rainbow-delimiters-syntax-table' can be nil. We handle this case by
skipping propertization if the syntax table is unset.

Closes https://github.com/purcell/emacs.d/issues/209
Pass the variable symbol to rainbow-delimiters-apply-color directly.

This means we do one concat and intern-soft less on every highlighted
delimiter, yielding an easy ~10% speed gain and less GC traffic.
Simplify rainbow-delimiters-delim-regex.
Release version 1.3.12.
Merge pull request #41 from jlr/no-global

Remove global-rainbow-delimiters-mode.
Update the readme.

The mode can't be used editor-wide as is anymore.