WEBrick has to bind proper host specified in `Capybara.server_host`
Results can now be sampled.

An instance of Result can now call #sample. This is delegated to Array#sample.
This allows a random result to be chosen.
This is useful if we want to check one of the results but with no particular preference as to which result.
Merge pull request #1161 from route/fix_server_host

Make `Capybara.server_host` working properly
Merge pull request #1162 from asmega/result_sample

Results can now be sampled.