Push fractional exponent up a little higher for less ambiguity

Test Plan: Tested locally and showed it to Erin who approved!

Auditors: peter
Better event handling for movablePoint and mouseLayer.

Summary:
In order to have "Click to add points" create the new point on mouse down
and demonstrate the correct drag behavior, some of the event handling in interactive
needed to be refactored. The mouseLayer now supports a wider range of mouse events
(and binds mouse move events to $(document) to provide identical behavior on touch
and browser devices) and movablePoint now has a "grab" method to allow for initial
grabbing.

Test Plan: Same as for D9434

Reviewers: eater, jack

Reviewed By: jack

Differential Revision: http://phabricator.khanacademy.org/D9436
Removed type="number" from input elements

Summary:
type="number" was causing problems for some inptus where the user
needed, for example, a period. All inputs now default to type="text". For
touch devices, we also set autocapitalize="off" to make the experience a little
smoother. Fixes T2592.

Test Plan: Try it out on a touch device. You probably need to run a breakpoint before the input element is rendered and set `window.Modernizr = { touchevents: true }` to make sure it defaults to mobile layout (if you run a SimpleHTTPServer from perseus/ke, it doesn't pick up Modernizr).

Reviewers: jack

Reviewed By: jack

Maniphest Tasks: T2592

Differential Revision: http://phabricator.khanacademy.org/D9972
Always use autocapitalization="off" for mathy inputs

Summary: Rather than just on touch devices, we now turn off autocapitalization
for all mathy inputs, such as for radicals and cube roots.
Changed 'constrainted' to 'constrained'
Change ft to m in the answer box

Auditors: peter
Merge branch 'master' of https://github.com/Khan/khan-exercises

# By Charles Marsh (4) and others
# Via Peter Collingridge
* 'master' of https://github.com/Khan/khan-exercises:
  Change ft to m in the answer box
  Changed 'constrainted' to 'constrained'
  Always use autocapitalization="off" for mathy inputs
  Removed type="number" from input elements
  Better event handling for movablePoint and mouseLayer.
  Push fractional exponent up a little higher for less ambiguity