Removed --latitude and --longitude options

- Removed --latitude and --longitude options and turned them into
  parameters for the --location option.
- If the --location option is not supplied at all, no location info will
  be added to tweets.
- If the --location option is supplied with no parameters, location info
  will be looked up by IP address.
- If the --location option is supplied with "latitude,longitude" as
  parameter, the given coordinates will be used as tweet location.
- The specs are updated to reflect these changes.