Correctly set working directory in setup.py

The setup.py script assumes that it is being run from the top-level
project directory with all filenames being relative to that location.
This may not always be the case, so we need to ensure that the working
directory is correctly set no matter where the script is invoked from.

Author: jerrykan

setup.py

@@ -159,6 +159,7 @@ def main():
           data_files=data_files)
 
 if __name__ == '__main__':
+    os.chdir(os.path.dirname(__file__))
     main()
 
 # vim: set filetype=python sts=4 sw=4 et si :