IdentityFile with quotes fails

Failing pulsar command:
```
HOSTFILTER=10.10.10.108 COMMAND='hostname -f' pulsar fuboo ci invoke -s gateway=''
```

Capistrano's `ssh.rb`:
```
      # load any SSH configuration files that were specified in the SSH options. This
      # will load from ~/.ssh/config and /etc/ssh_config by default (see Net::SSH
      # for details). Merge the explicitly given ssh_options over the top of the info
      # from the config file.
      ssh_options = Net::SSH.configuration_for(server.host, ssh_options.fetch(:config, true)).merge(ssh_options)

      # Once we've loaded the config, we don't need Net::SSH to do it again.
      ssh_options[:config] = false
```

Net-ssh: http://net-ssh.github.io/net-ssh/