Pin dependencies to ~> x.y
(GH-24) Remove Vagrant.require_plugin

Previously (on Lost), The Oscar templated Vagrantfile had an explicit
`Vagrant.require_plugin` invocation for Oscar. This was primarily needed
for development purposes and was not strictly needed for normal
operation. In Vagrant 1.5 #require_plugin was deprecated entirely, so
it's about time this was removed.
[gemspec] Pin dependencies to ~> x.y
Merge branch 'defect/master/gh-24-remove-vagrant-require'