Updated IOCextractor to leverage python-cybox v2.0.0

I updated the IOCextractor to leverage python-cybox v2.0.0, which enables the output of CybOX v2.0 content. The output of CybOX 2.0 content is optional, following the conventions established for OpenIOC output. The following changes have been made:
* Removed cybox folder containing python-cybox v1.0
* Added optional import for python-cybox
* Added version check for python-cybox, requiring at least v2.0
* Updated README to indicate python-cybox requirement
* Added a .gitignore to ease development and interaction with git

I have tested this code out on Windows 7 64bit and OSX 10.8.4. Let me know if there are any issues and thank you for supporting the output of CybOX with the IOCextractor!