Merge pull request #12 from ebfe/fix-build-master

Adapt to removal of ~str.
make main.rs the crate root for tests too
refactor LetVisitor to use ExprTypeVisitor
fix recursive search bug when searching let stmts
find enum methods
fix global searches - e.g. ::std::io::fs::...
StrBuf was renamed to String
set exit status != 0 in error paths
Merge pull request #14 from ebfe/exit_status

set exit status != 0 in error paths
Merge pull request #13 from ebfe/strbuf-string

StrBuf was renamed to String
to_strbuf -> to_string
to_owned -> to_string