More operations between Natural, Integer, Rational and builtin types

As discussed in #52 it is currently a bit messy to compute the remainder of a Natural by a u32 and obtain a u32, though it is possible by converting Natural to usize first. This issue is for adding more conversions and operations involving a mixture of algebraeons Natural, Integer and Rational types with rusts builtin u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128 and isize where appropriate.

• TryInto<u8 ... u128, usize, i8 ... i128, isize> for Natural (#55)
• TryInto<u8 ... u128, usize, i8 ... i128, isize> for Integer (#55)
• TryInto<u8 ... u128, usize, i8 ... i128, isize> for Rational (#81)
• Natural % T -> T for T = i8 ... i128, isize,u8...u128,usize
• Integer % T -> T for T = i8 ... i128, isize,u8...u128,usize

Any others to include on the list?