Fix to handle ssh options

Added the ability to use options provided in the initialisation(Net::SSH::Session.new).

One use case for the change would be when authenticating using public-private key files. The base library (Net::SSH) supports such mechanism, the provided options hash is transparently passed down to base libraries.

Below are few ways in which suggested change enables initialisation.

using host,username & password
`session = Net::SSH::Session.new('host', 'user', :password=>'password')`

using host, username  & private key
`session = Net::SSH::Session.new('host', 'user', :keys=>'/path/to/private/key/file')`

loading default openssh config file(~/.ssh/config)
`session = Net::SSH::Session.new('host', 'user', :config=>true)`