Raise ArgumentErrors in Math.fibs
Raise ArgumentErrors in Integer#factors
Don't use should when testing for ArgumentErrors
Remove support for list comprehensions (it's confusing at not very necessary)
Merge branch 'develop' into feature/raise-errors
Raise exceptions instead of returning nils and doing other weird stuff (fix #23)
Raise exceptions when Arrays contain non-Numeric objects (fix #25)
Merge branch 'develop' into feature/raise-errors

Conflicts:
	spec/math_spec.rb
Bring Array#numerics back

It's useful for preparing Arrays to work with methods that require Arrays of
Numerics.
Merge branch 'feature/raise-errors' into develop