Merge pull request #855 from sainaen/fix_849

Replace `sendRequest()` calls with `sendMessage()` ones in marks.coffee
Add multi-character mapping support.

Prerequisite scaffolding for "quick makrs" feature.

Test plan:

* Added various mappings like "abcd", "cdef", "dekg", verified that they
  execute appropriately when something like "bcdekg" is typed.
* Console logging.