Upgrade capybara to 1.1.4

This brings capybara's json parsing dependencies up to date with
the latest security fixes just in case someone is not exluding the
:test group of gems when running deployinator on a public server.
Upgrade json to 1.7.7

Fixes some security vulnerabilities:

https://groups.google.com/forum/?fromgroups=#!topic/rubyonrails-security/4_YvCpLzL58
Upgrade rack to 1.5.2

Fixes some security vulnerabilities:

https://groups.google.com/forum/#!msg/rack-devel/mZsuRonD7G8/DpZIOmMLbOgJ