development: &default
  adapter: postgresql
  database: <%= app_name %>_development
  encoding: utf8
  host: localhost
  min_messages: warning
  pool: <%%= Integer(ENV.fetch("DB_POOL", 5)) %>
  reaping_frequency: <%%= Integer(ENV.fetch("DB_REAPING_FREQUENCY", 10)) %>
  timeout: 5000

test:
  <<: *default
  database: <%= app_name %>_test

production: &deploy
  encoding: utf8
  min_messages: warning
  pool: <%%= [Integer(ENV.fetch("MAX_THREADS", 5)), Integer(ENV.fetch("DB_POOL", 5))].max %>
  timeout: 5000
  url:  <%%= ENV.fetch("DATABASE_URL", "") %>

staging: *deploy

development: &default
  adapter: postgresql
  database: <%= app_name %>_development
  encoding: utf8
  min_messages: warning
  pool: <%%= Integer(ENV.fetch("DB_POOL", 5)) %>
  reaping_frequency: <%%= Integer(ENV.fetch("DB_REAPING_FREQUENCY", 10)) %>
  timeout: 5000

test:
  <<: *default
  database: <%= app_name %>_test

production: &deploy
  encoding: utf8
  min_messages: warning
  pool: <%%= [Integer(ENV.fetch("MAX_THREADS", 5)), Integer(ENV.fetch("DB_POOL", 5))].max %>
  timeout: 5000
  url:  <%%= ENV.fetch("DATABASE_URL", "") %>

staging: *deploy

Remove database host config for Linux support
Remove database host config for Linux support

Extracted from https://github.com/thoughtbot/administrate/pull/359.
Issue first reported in https://github.com/thoughtbot/administrate/issues/296.

Problem:

Ubuntu (and possibly other Linux distributions)
don't recognize `localhost` as a valid host parameter
in `config/database.yml`.

Running `bin/setup` gives them the error:

```
Couldn't create database for {"adapter"=>"postgresql",
"database"=>"administrate-prototype_development",
"encoding"=>"utf8",
"host"=>"localhost",
"min_messages"=>"warning",
"pool"=>2,
"timeout"=>5000}
```

Solution:

Remove the `host` key from `config/database.yml`.

Without the `host` key, OS X defaults to `localhost`
and Ubuntu defaults to its Linux-y equivalent.

[closes #683]
