Add floating point support to lexer

- There are three ways to specify a float with
  exponential notation and positive exponent:
  1E2, 1E+2 and 1e+2

- However, 1e2 will mean the vector (0, 1, 0)
Add basis vectors to the lexer
Add comments for v and s functions
Add initial version of MathML output converter
Improve MathML converter
Added MathJax as rendering engine.

It's so pretty I want to cry.
Tune answer output a bit
Make the UI just a bit prettier

Fixes #5
Break NUMBER pattern to two lines
Merge remote-tracking branch 'origin/master'