Haxe doesn't support directly overloading +=, -= operators and will create a
new object. (issue #2)
Removed the operator overloads for all +=, -= (surprised they didn't fail
at compile time, but apparently the compiler doesn't care for the most
part what you put in
the @:op macro, e.g. --*).
Refactored all +, - operators to call addWith, subtractWith and cut down
on repetition.
Fixed a (some what major) bug where addWith, subtractWith were returning
the rhs instead of the lhs. The code was never hit before due to the issue
mentioned above.
Merge branch 'master' of https://github.com/tbrosman/vtg-math