Update transmute and forget to use std::mem instead of std::cast
Merge pull request #39 from dguenther/update_cast

Update transmute and forget to use std::mem instead of std::cast
extern api use now StrBuf
update travis, use official Rust distribution
remove all uses of ~str
update to last Rust
- ~Str -> StrBuf
update to last Rust
- StrBuf -> String