Fix Gemfile requires.

Hi Matt,
I installed the tool in a clean environment and "gt" command didn't work.
```
elkirk:~ stefanofontanelli$ gt --help
/Users/stefanofontanelli/.rvm/rubies/ruby-1.9.3-p374/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- net/ssh (LoadError)
	from /Users/stefanofontanelli/.rvm/rubies/ruby-1.9.3-p374/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
	from /Users/stefanofontanelli/.rvm/gems/ruby-1.9.3-p374/gems/gaptool-client-0.3.2/lib/gaptool-client.rb:7:in `<top (required)>'
	from /Users/stefanofontanelli/.rvm/rubies/ruby-1.9.3-p374/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
	from /Users/stefanofontanelli/.rvm/rubies/ruby-1.9.3-p374/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
	from /Users/stefanofontanelli/.rvm/gems/ruby-1.9.3-p374/gems/gaptool-client-0.3.2/bin/gt:16:in `<top (required)>'
	from /Users/stefanofontanelli/.rvm/gems/ruby-1.9.3-p374/bin/gt:19:in `load'
	from /Users/stefanofontanelli/.rvm/gems/ruby-1.9.3-p374/bin/gt:19:in `<main>'
	from /Users/stefanofontanelli/.rvm/gems/ruby-1.9.3-p374/bin/ruby_noexec_wrapper:14:in `eval'
	from /Users/stefanofontanelli/.rvm/gems/ruby-1.9.3-p374/bin/ruby_noexec_wrapper:14:in `<main>'
```

I fixed the requires then the script start to work.