Implement a simple build system
Implement FromPrimitive and add (some of) RandBigInt
Implement ToBigUint using macro from num::bigint
Make test build the lib as well

This way you can do `make test && make install`
Implement more traits

 - Derive Clone, Eq, Ord, TotalEq, TotalOrd, and Zero from Mpz.
 - Implement One, FromStr, and part of num::Integer
Implement a few more operations

 - bits
 - divides
 - bitand
 - rem
 - shr