Remove db files
Add db files to .gitignore
Download DB files during TravisCI build
Remove global lookup service in favor of protocol

The Lookupable protocol can be used to lookup an ip address. Furthermore
the multi-lookup-service function returns the combined information from
multiple db files.
Removes the download of the ip v4 db files

Lookup only uses the ip v6 db files. In my tests the returned data from
the ip v4 db files was identical.
Bumps version to 0.2
Change README to reflect changes in version 0.2
Merge pull request #17 from bertschneider/issue-7

Issue 7