(POOLER-73) Restructure tests to unit and integration directories

Previously all of the spec tests for VM Pooler were all together in the specs
directory.  However some tests require a working local Redis server to operate
and other instead mock all external dependencies.  This commit splits the test
files between unit and integration, where integration tests require a working
Redis instance, and unit tests do not.  This commit also removes the root
`vmpooler` directory as it is not required.  The tests rake test still operates
correctly.

This commit also adds the mock_redis library for testing for the pool_manager.

spec/unit/pool_manager_spec.rb

@@ -1,5 +1,6 @@
 require 'spec_helper'
 require 'time'
+require 'mock_redis'
 
 describe 'Pool Manager' do
   let(:logger) { double('logger') }