Merge remote-tracking branch 'fizx/solr4' into solr4

Conflicts:
	sunspot/lib/sunspot/version.rb
Use per-environment cores, and a default, with shared instanceDir and separate dataDir
Update Gemfiles to the latest Bundler requirements
Correctly prepare the Solr installation in an app for multicore
Update to Solr 4.2.0
Make sure travis is testing with rubygems < 2.0 for now
Clarify version support in Travis build matrix
Merge pull request #364 from fizx/solr4

Solr4 compatibility
Fix rails 2.3.16 gemfile for ruby 2.0.0

This allows the travis specs to pass on rails 2.3.16 / ruby 2.0.0.
Update build matrix excludes for ruby 2.0.0