Added CI tasks for each gem in dm-more.
Added CI tasks for each gem in dm-more.

*  Changed all Rakefile references of 'specs' to 'spec'.
*  Moved merb_datamapper/specs to merb_datamapper/spec.
*  Added 'ci:*' rake tasks for CI.
*  Updated the gems list in Rakefile.

datamapper/dm-is-tree