Fixes an issue on Travis

This was only reached when PATH contained relative paths.
Factors get_string() in C code
Passes binary and databasepath through get_string

This allows bytes to be passed in on Python 3.
Adds unicode_ for Python 3 compatibility
Adds encoding='utf-8' to open() calls

I added this to rpaths 0.3 and it's great.
Fixes more unicode/bytes problems
Correctly packs intermediate symlinks
Adds newline='\n' to some open() calls

When writing a script file, we want the line ending to be LF.