Generate reference to the database in the cache template for all envi…

[orbanbotond]

Fix #278

The problem:
When we run the bundle exec rails solid_cache:install, it generated a cache.yml file which contains the reference to the cache database only for production mode.
(Personal Note: As I was testing the cache in development, I was expecting that the generated file would be perfect for all environments. Then I would turn on the caching for the development environment in the development.rb by config.cache_store = :solid_cache_store if I wanted to. But I was surprised. My eyes just jumped over the missing database:... part in the cache.yml file, so I spent about 20 minutes figuring out what was wrong. If we multiply that 20 minutes by 10000 devs who are struggling, then that is a lot of lost hours ~3300)

The solution:
Generate a ready-to-use cache file.

This decision is up to you (37signal) guys :) I just want to be helpful.

Some other guys were also struggling with this issue:
https://www.reddit.com/r/rails/comments/1gws1fp/help_needed_with_solid_cache/

[AliSepehri]

I agree, not having solid_cache setup for development is confusing. But this PR changes requires also a change in Rails repo to consider cache in database.yml file otherwise it will fail by default.