Tokenizer now handles numbers with exponents, which fixes matrices not
working if they contain an exponential number. This was discovered when
a gradient wouldn't work because it contained a matrix with a number
like 4e-1. 
Renamed excessWidth / excessHeight to remainderWidth / remainderWidth
throughout as seems more appropriate, and added a method in the
controller
interface to inform the controller what the remainder width / height
values are. The tpsvg:stretch-to-excess attribute is now changed to
tpsvg:stretch-to-remainder.