Ruby 2 support

This pull request keeps this long dead project alive on ruby 2.0.

`bundle exec rake test:surface` now passes all tests on ruby 2.0.0 and 1.9.3 with no deprecations.
`bundle exec rake test:deep` fails only one test on ruby 2.0.0 due to a change in the included OpenSSL ciphers... probably not a big deal:

```
test_options(SOAP::SSL::TestSSL) [.../soap4r/test/soap/ssl/test_ssl.rb:45]:
<-2130703361> expected but was
<-2097019905>.
```