Add spec to cover all `rescue_from :all` exception scenarios
Add spec to cover all `rescue_from :all` exception scenarios

Added another spec to demonstrate current behavior when attempting to rescue from a non-StandardError exception. As of now, rescue_from :all only rescues StandardError exceptions, so when a non-StandardError exception is encountered, Grape will not trap the error.

intridea/grape,ruby-grape/grape,dblock/grape,dslh/grape