Fixed command-line file search interface

argparse complains if a search query is specified using spaces to separate
each search modifier (because argparse assumes that the space means the end of
the argument). Changed to a comma-separated list of search modifiers.
Added optional offset argument to the file_search method

The offset allows for pagenation of search results. This pagenation must be
done manually, but hopefully in the future it can be handled programatically
by this script
Updated README in accordance with CLI changes
Added pagination to file searching

Added pagination ability based on VirusTotal private API documentation. Still
needs to be tests
Added pagination to file searching

Added pagination ability based on VirusTotal private API documentation. Still
needs to be tests
Merge branch 'search-pagination' of https://github.com/adrianherrera/virustotal-api-script into search-pagination

Conflicts:
	vt_driver.py