create type for irrationals, reconfigure iterators

[simonbyrne]

This is not quite ready to be merged, but I thought I would get your thoughts. It changes a few things to allow for infinite length expansions for irrational numbers.

Still to do:

• Add a QuadraticSurd type for repeating expansions.
• Docs and tests.

[anthonyclays]

Great work! I took the liberty of looking over your code (John Myles White said he isn't actively supporting this package anymore).

I very much like the idea of finite and irrational continued fractions as different types. Your compute! function is also a great idea to lazily calculate to a desired precision.

Thanks for all the work!

[anthonyclays]

Why does this need a generic parameter T? Isn't that parameter implied by CF?

[simonbyrne]

You might not always want them to be the same, e.g. you might want T to be BigInts (to avoid overflow), whereas the iterator might just give you Ints.