UTF-8 file paths error on python 2

Created by: jrbenito

Python 2 needs utf-8 decode since it uses 'ascii' decode by default.

Fixes #291 (closed)

Before:

$ python --version ; echo ; bin/solaar show
Python 2.7.12

Traceback (most recent call last):
  File "bin/solaar", line 42, in <module>
    init_paths()
  File "bin/solaar", line 29, in init_paths
    prefix = _path.normpath(_path.join(_path.realpath(sys.path[0]), '..'))
  File "/usr/lib/python2.7/posixpath.py", line 73, in join
    path += '/' + b
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 44: ordinal not in range(128)

$ python --version ; echo ; bin/solaar show
Python 3.5.2

solaar: error: Logitech receiver not found

After:

$ python --version ; echo ; bin/solaar show
Python 2.7.12

solaar: error: Logitech receiver not found

$ python --version ; echo ; bin/solaar show
Python 3.5.2

solaar: error: Logitech receiver not found

Signed-off-by: Josenivaldo Benito Jr jrbenito@benito.qsl.br