add support for AsciiMath input

* Add note to Readme.md
* don't suppress MathML output

Change-Id: I15cb2d1cb0533a2fa0e21012198387501a3b42ea
Fix: Correct link to Math submodule

A commit that was only submitted for review but not yet approved
was linked as reference for the Math submodule.

Change-Id: I17cb083abfe34859980ea59d23d5ee6e3a57ff32
Fix form, improve startup message

* Fix the for to use the q parameter instead of tex (not sure that this change
  is a good idea though)

* Don't point users to phantom backends where the form won't be found; point
  them to the master mathoid port.

Change-Id: Ia9b08e8561bcd74a324b8489f51f0d63861d69ee