This PR fixes the issue(s) described in #713. To fix the logger option
issue, I simply delete `Request.options[:logger]` when dumping. To fix
the proc parser issue, I delete `Request.options[:parser]` if and only
if `Request.options[:logger]` is a proc. If `Request.options[:logger]`
is a regular class, `Marshal.dump` should proceed as normal. This should
not affect the `Marshal.dump` behavior described in issue #143 and fixed
by PR #618.
I have added a feature spec to make sure marshalling the request
works as intended, as well as a unit test to ensure
`Marshal.load(Marshal.dump(req))` works as it should.
