v0.5.3

Released to PyPI

• Quite a few docstring changes
• ExifToolHelper's get_tags() and set_tags() checks tag names to prevent inadvertent write behavior. See Documentation on Exceptions to get an idea how the change makes using PyExifTool safer!
• Renamed a few of the errors to make sure the errors are explicit
  • ProcessStateError -> ExifToolProcessStateError
  • new ExifToolExecuteException for all execute() related errors which returns stdout, stderr, returncode, cmd of offending command
    • OutputEmpty -> ExifToolOutputEmptyError
    • OutputNotJSON -> ExifToolJSONInvalidError
• ExifToolHelper() has some static helper methods which can be used when extending the class (ExifToolAlpha.set_keywords_batch() demonstrates a sample usage).
• setup.py tweaked to make it Beta rather than Alpha
• ExifToolAlpha.get_tag() updated to make it more robust.
• Fixed ujson compatibility
• Cleaned up and refactored testing.