Additional support for UUIDs, 64 bit binaries, and different endians

My company (Skillz) has taken on your library and updated it to fit some of the binaries we deal with. Included in this pull request are the following changes,

- Support for reading UUIDs from the load commands
- Support for 64bit executables
- Support for different endian binaries and executable
- Some minor bug fixes

Hope you find this helpful.