* Adds decoration to the verifier errors.
example:
function %bad(i32) fast {
ebb0(v0: i32):
brnz.i32 v0, ebb1
return
^~~~~~
verifier inst1: Internal return not allowed with return_at_end=1
ebb1:
trapz.i32 v0, user6
return
}
Fixes#68
* Making it so that pretty_function_error and write_function_plain are both private.
* Changes write_ebb to decorate_ebb.
Adds documentation line to decorate_function.
* Removing Cargo.toml lib/serde addition
* Add serde functionality into lib.
* Fix so code is compatible with Rust version 1.25.0.
* Move ser/de functions to utility file, update description, remove borrow from arms.
* Remove commented out code.
