Allow user to use a custom pricing file by placing a file to ~/.libcloud/pricing.json.
Add cli utility for updating pricing file.
Add argparse dependency for Python < 2.6 and >= 3.1 and <= 3.2.
Add download_pricing_file function to libcloud.pricing module.
Remove CLI stuff since it will be part of a separate PR.
Revert "Add argparse dependency for Python < 2.6 and >= 3.1 and <= 3.2."

This reverts commit a62b97a098441603832deb239307a8cd7cf53029.
Fix a typo.
Update changes.