improved error handling

[transcendental] sqrt: change error type from () to &'static str. (#7)

* Closes #6: Resolve this by printing an error if an overflow occurs in `sqrt`due to small numbers.
* Add test that shows the approximate lower bound of working values for I32F32
* version bump: v0.5.5

initial fork release

adds support for substrate-specific traits
adds transcendental functions. Mainly for signed types so far.