Split out database testing into separate CI runs

Fixes calagator#53

Previously, we were running `rake spec:db:all` on CI, which ran our test
suite using mysql, postgresql, and sqlite3, but didn't provide very much
visibility into which databases were passing or failing. This change
moves to using Travis to set a DB environment variable and then running
`rake spec` under each environment.

.travis.yml

@@ -18,8 +18,16 @@ rvm:
   ## Rubinius is not compatible, see Gemfile for details.
   # - rbx-18mode
   # - rbx-19mode
-script:
-  - export DBUSER_MYSQL=root
-  - export DBUSER_POSTGRESQL=postgres
+env:
+  - DB=mysql
+  - DB=postgresql
+  - DB=sqlite
+before_install:
+  - ruby ci/copy_database_config.rb
+before_script:
+  - mysql -e 'create database calagator_test;'
+  - psql -c 'create database calagator_test;' -U postgres
+  - bundle exec rake db:migrate
   - cp "config/secrets.yml.sample" "config/secrets.yml"
-  - bundle exec rake spec:db:all --trace
+script:
+  - bundle exec rake spec --trace

ci/copy_database_config.rb

@@ -0,0 +1,6 @@
+require 'fileutils'
+
+which_config = "ci/database.#{ENV['DB'] || 'sqlite'}.yml"
+
+puts "Copying database configuration for CI: #{which_config}"
+FileUtils.cp which_config, 'config/database~custom.yml'

ci/database.mysql.yml

@@ -0,0 +1,5 @@
+test:
+  adapter: mysql2
+  database: calagator_test
+  username: travis
+  encoding: utf8

ci/database.postgresql.yml

@@ -0,0 +1,4 @@
+test:
+  adapter: postgresql
+  database: calagator_test
+  username: postgres

ci/database.sqlite.yml

@@ -0,0 +1,5 @@
+test:
+  adapter: sqlite3
+  database: db/test.sqlite3
+  timeout: 500
+