Patch exists? where scopes are used

AcitveRecord 3 will delegate exists? to the Relation rather than
ActiveRecord::Base if it is called on a scope, meaning that
SomeModel.some_scope.exists? will run a query on the master
Correct method name in test
Test Scope.exists? on Rails 2 and 3
Merge pull request #4 from zendesk/sean/patch_ar3_exists

Patch ActiveRecord 3 `exists?` with scopes
v2.7.5
install rake tasks for building and releasing
upgrade appraisals
support default-on-slave for .pluck
fix rails 3.0/pluck
Merge pull request #7 from zendesk/ben/support_pluck

Support .pluck on slave by default
adding debugger to gemfiles
rails32 :include of has_and_belongs_to_many associations -> default slave

This also contains a fairly large refactoring of how we pull off monkey
patching for slave-by-default stuff.
Merge remote-tracking branch 'origin/master' into ben/support_has_many_include_on_slave

Conflicts:
	gemfiles/rails32.gemfile
	lib/active_record_shards/default_slave_patches.rb
	test/connection_switching_test.rb
Merge pull request #8 from zendesk/ben/support_has_many_include_on_slave

Support has_and_belongs_to_many :include on slave by default
v2.8.0
Merge branch 'master' into rails4_support

Conflicts:
	Gemfile
	active_record_shards.gemspec
	lib/active_record_shards/default_slave_patches.rb
	test/schema.rb