Set site.email to eng@causes.com

This configuration value is used by the theme we are currently using to
generate the URL for the Gravatar in the site header. Setting it to
eng@causes.com to generate a non-default Gravatar for the blog.

Change-Id: Id0dca3e5e8df932f39b1646bab43f6e21b6c64b6
Reviewed-on: https://gerrit.causes.com/22425
Tested-by: Joe Lencioni <joe.lencioni@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>