Restrict monospaced fonts to serif ones, i.e. Courier family.
Prefer Courier 10 Pitch for monospaced serif on Linux.
Merge pull request #52 from cben/mono-font

Restrict monospaced fonts to serif ones, i.e. Courier family.
New firebase, firepad: bugs, better mark-based cursors, CM 4 support.
New deps, notably CM 4.3
(4.4 breaks firepad: https://github.com/firebase/firepad/issues/142)