ThinkingSphinx::Search#respond_to? handles mask methods.

Closes #747.
Ensuring property queries avoid empty join values.

Closes #734.
Add clear method and no-index option for start to ThinkingSphinx::Test.
Setting for disabling real-time index callbacks.
Ignore the local tmp folder.
Merge branch 'develop' into develop_respond_to

Conflicts:
	spec/thinking_sphinx/search_spec.rb
Added  basic unit  test and  proper 'method'  call handling  for methods
delegated to masks / context.