api: Fix unicode issue when trying to add \n to the read file

Without this I get errors like:

filename_x: problem decoding source

Digging deeper, and adding traceback printing I see the error is:

Traceback (most recent call last):
  File "/Library/Python/2.7/site-packages/frosted-1.1.2-py2.7.egg/frosted/api.py", line 75, in check_path
    codestr = f.read() + '\n'
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc4 in position 14385: ordinal not in range(128)