(fix) removed deprecated syntax for lifetime in traits

I don't really understand whats going on, but removing 'static
lifetime allows this library to compile and tests to pass. However
104 tests were ignored.

This fixes the error:
src/encoding/types.rs:105:25: 105:32 error: expected ident, found `'static`
src/encoding/types.rs:105 pub trait StringWriter: 'static {