Updated net-scp and net-ssh deps in vagrant.gemspec

Veewee and a few other gems install newer versions of net-ssh and net-scp than what Vagrant had specified.

I changed the specs and from some basic functionality tests, things seem to work fine.

Before, running `vagrant` or any subcommand of it resulted in a `(Gem::LoadError)` that complained about conflicts:

<pre>
/Users/nick/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/rubygems/specification.rb:1637:in `raise_if_conflicts': Unable to activate net-scp-1.1.0, because net-ssh-2.2.2 conflicts with net-ssh (>= 2.6.5) (Gem::LoadError)
	from /Users/nick/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/rubygems/specification.rb:746:in `activate'
	from /Users/nick/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/rubygems/specification.rb:780:in `block in activate_dependencies'
	from /Users/nick/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/rubygems/specification.rb:766:in `each'
	from /Users/nick/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/rubygems/specification.rb:766:in `activate_dependencies'
	from /Users/nick/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/rubygems/specification.rb:750:in `activate'
	from /Users/nick/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/rubygems.rb:1232:in `gem'
	from /Users/nick/.rbenv/versions/1.9.3-p392/bin/vagrant:22:in `<main>'
</pre>