Lock version of database cookbook

A release of mysql-chef_gem broke the database cookbook because
it removed the default recipe which the database cookbook was using.
Since the database cookbook did not lock versions of mysql-chef_gem,
it pulls the latest mysql-chef_gem cookbook and fails.

An update to the database cookbook was released to fix this, however
Berks dep solving is getting the latest mysql-chef_gem and an older database
cookbook for the webapp test cookbook.
Merge pull request #2631 from opscode/jdm/kitchen-tests

Constrain version of database cookbook
Convert knife specs to let bindings
Add specific error messaging for SSL errors to knife

Knife now gives an error message like this when an SSL error occurs:

```
ERROR: Could not establish a secure connection to the server.
Use `knife ssl check` to troubleshoot your SSL configuration.
If your Chef Server uses a self-signed certificate, you can use
`knife ssl fetch` to make knife trust the server's certificates.

Original Exception: OpenSSL::SSL::SSLError: SSL_connect returned=1
errno=0 state=SSLv3 read server certificate B: certificate verify failed
```