Add functions for thing-at-point
Hardcode delimiters in cm-{forward|beginning|end}-* functions

The partial delimiters are hardcoded as well, so...
Add cm-markup-at-point and cm-bounds-of-markup-at-point
Use cm- prefix on markup type symbols.
Remove space after 'bindings' addition in the README.
Implement cm-accept/reject-change-at-point
Update README with key binding C-c * a and a section on font lock.
Fix cm-accept/reject-change-at-point

* Inhibit C-g when reading a character and add (q)uit as an option to replace it
* Fix keymap
* Add checks to the markup insertion functions to make sure we're not already inside a change