net_http.rb: StubSocket needs continue_timeout for aws-sdk

For Ruby 2.0
See:
https://github.com/aws/aws-sdk-ruby/blob/7c4ea3d6004068e4905994be91de459651a96116/lib/aws/core/http/connection_pool.rb#L127

and:
https://github.com/ruby/ruby/blob/v2_0_0_0/lib/net/http.rb#L725
Merge pull request #278 from godfat/continue_timeout

net_http.rb: StubSocket needs continue_timeout for aws-sdk