Use boost::unordered_map, fix build issues on OSX

- Replace std::try::unordered_map with boost::unordered_map
- Respect LIBRARY_PATH environment variable
- Search .dylib libraries on OSX
- Add *.pyc to .gitignore
fix copy&paste variable name error in Call(thread)
rename sysex_to_sequence() to sysex_to_bytearray()

now that we require Python >= 2.6, sysexes are always bytearrays.
support SysEx strings in ASCII notation