Rakefile simplification, addition of spec.opts
Rakefile simplification, addition of spec.opts

* Simplified Rakefiles for the remainder of the DM
  plugins (mirroring changes in in commits 427d146
  and ce9eff8). This should also avoid redeclaration
  of constants and 'autorequire = PLUGIN' warnings.
* Added rake and rake clobber tasks.
* Made :spec the default task for all plugins.
* Added spec.opts files, with color for autotest.

* Made all dm-core requirements >= 0.9.0.
* Incremented Merb version required (0.9.3) for
  merb_datamapper plugin.
* Reordered list of gems in root Rakefile.

ar-dm/ardm-types,lgierth/dm-types,troygnichols/dm-types,datamapper/dm-types,engineyard/dm-types