This commit adds the Data Science Toolkit as a lookup type.  The DSTK behaves identically to the Google Maps API with the exception that it can be run behind your own firewall.  More information about this tool can be found here: http://www.datasciencetoolkit.org/
Updated README to include dtsk information
Merge pull request #475 from ejhayes/master

Support for Data Science Toolkit (DSTK) lookup.