Only display replacement cookbook info if present.

When viewing a deprecated cookbook and a deprecated cookbook partial, only
display the replacement cookbook if there is a replacement cookbook. For
example, if a cookbook is deprecated and then the replacement cookbook is
deleted, there could be a missing replacement.
Add feature specs for various deprecated states

Whether deprecated w/ a replacement or when a replacement is deleted, the
content about the deprecation changes. This add specs about what is expected to
be displayed and what is not expected to be displayed.
Simplify the cookbook deprecated state view logic.
Merge pull request #616 from opscode/cookbook_deprecation

Only display replacement cookbook info if present.