Arbitrary precision numbers

[danilopedraza]

Right now the language only has 64-bit signed integers. I need to add arbitrary precision numbers. This includes:

• [x] BigInts
• [x] BigDecimals
• [x] Fractions

I'm not sure if I should mix BigInts and BigDecimals into one type, or have them separated.

[danilopedraza]

I decided that I'm going to add this feature through libraries. I considered one option: the num library. There is also a library called bigdecimal-rs which was originally meant to be included in num. I need it since num does not have BigDecimals.

[danilopedraza]

Also, I'm going to make integers and decimals different types.

[danilopedraza]

Pending tasks:

• [x] Implement pending Fraction operations
• [x] Fix Integer's exponentiation implementation (#40)

[danilopedraza]

Done.