Rename :map_view to :map

Looks like this changed a while ago and the documentation was never updated: https://github.com/clayallsopp/formotion/search?q=map_view&ref=cmdform
Update rake file to modern rm 2.0
Adds WebLinkRow with spec.
Adds web_link to the list of cell types.
Allow WebLinkRow to accept an NSURL and not just a string.
Add functional test for WebLinkRow
Merge pull request #174 from markrickert/web-link-row

Web link row
Merge pull request #173 from markrickert/fix-rowtypes-readme

Rename :map_view to :map