Revert "Don't hard-code version in the elisp: rely on tags instead".

It breaks package-install-from-buffer.
Remove unneeded require.
Use standard form of the footer comment.
Fix docstring style errors reported by checkdoc.
Properly tear down the mode when changing major mode.

Unpropertize is now run when changing major mode, so stale highlighting
will not carry on from the previous major mode.
Fix a bug that caused (rainbow-delimiters-syntax-ppss 1) to return nil.
Revert a part of 3dfd3fa9b that shouldn't be changed in the first place.
Release version 1.3.7.
Wrap rainbow-delimiters-{un,}propertize-region with with-silent-modifications and with-syntax-table.

This avoids constant variable binds in the loop and ensures all internal
function are run with the same environment.
Make rainbow-delimiters-outermost-only-face-count customizable.

Fixes #24.
Correct the prefix of the rainbow-delimiters-faces group.
Add code to highlight mismatched closing delimiters.

Fixes #27.
Reduce the amount of copy and paste in rainbow-delimiters-propertize-region.
Highlight correctly even in presence of these evil 'intangible' properties.
Add lisp-interaction-mode to rainbow-delimiters-escaped-char-predicate-list.