Fixed rebuild! when there is default_scope with order declared

* Also added test for rebuild! action
* Fixes #165
* Fixes #91
Stop using prerelease bundler on Travis builds.
Adjusted rubies to test and test script.
Move rspec-rails declaration to the Gemfile and improve the gemspec for license, etc.
Stop messing with the load path.
Allow bundle exec rake to work.

Require rspec/rails not rspec
Optimize move_to for large trees. Restrict Update query to only modify records which have values lft,rgt,parent_id that change.
fixed type.
Switched constraint from ( <> and <> and <> ) to not ( = and = and = )
CI against mysql and postgresql too.

Use https rubygems source.
DRY up Gemfiles and make rake spec run against all Rails versions.

Move code to more logical places.

Define better versions and use railties too.
Switched build script from rake to rspec.
Merge pull request #171 from ericsmith66/master

Performance Issue with move_to
Document next release.
Test Ruby 2.0.0 not 2.0 as the alias updated.
Merge pull request #174 from dosire/document-changes-for-2-1-6

Document next release.
remove some wordy lines of code and changed #move_to_root implementation
Prefer 2.0.0/1.9.3 to 1.8.x variants. Require database_cleaner.
Rewrite specs to check inclusion in array rather than absolute equality.
Fix test for JDBC