Rename spec/matchers to spec/dsl
include_content_type(:any) always passes
Replace be_valid_json with be_a_collection
Better description for filter with compare Proc
Warn when filter or attributes hit an empty array
Remove unnecessary run_if

Rather than having half-baked matchers, it's the responsibility of
the caller not to invoke a matcher if it's not required to pass.
Bump version to 0.5.0