feat[patch]: support for patch verb

[jakeyheath]

This PR adds support for the "patch" verb. This would allow you to be able to call:

response = SsrfFilter.patch(params[:url]) # throws an exception for unsafe fetches

This PR resolves #38 . I needed to also update the maximum version of "psych" because 4.0 introduced a breaking change for YAML files with dates in them: ruby/psych#489

[coveralls]

Coverage remained the same at 100.0% when pulling 0e8cbfe on jacobrheath:heathj/patchverb into ebb24a1 on arkadiyt:master.

[arkadiyt]

I tried pushing a commit to this branch but am having some issues with my github setup. Could you try adding a line here to pin rexml to 3.2.4? It might resolve the ruby 2.0 failure

[jakeyheath]

Sure, let me try

[jakeyheath]

@arkadiyt nice job! That seemed to have done it. Let me know if you have any other comments.

[arkadiyt]

Looks great, thanks for the contribution

If you need this for a project let me know and I can push a new version to rubygems

[jakeyheath]

O great, no rush. We are using it in a project, but its not super time-sensitive. Thanks for merging!