use eventmachine at github master

because eventmachine 1.0.3 cannot compile on ruby 2.2.0

ttps://github.com/eventmachine/eventmachine/commit/c95f1e11c2c0f0e23cd9d4ac2a9c7a75afe54710
Merge pull request #195 from onk/feature/support_ruby_2_2_0

use eventmachine at github master
Make database adapter selectable for production

- Install both `mysql2` and `pg` gems by default
- Add `BUNDLE_WITHOUT` option in app.json
- Update setup instructions in README.md
- Fix typo: database.yml.potgresql -> database.yml.postgresql
Select db adapter based on configuration or DATABASE_URL
Copy database.yml before build
Copy database.yml on build
Copy database.yml before/in build
Include sqlite3 on development/test
updated Gemfile.lock
remove traial code
Merge pull request #199 from ayumin/db-adapter

Select database adapter based on configuration
include pg
add pg in production
Changed Heroku Button's template
Merge branch 'master' into heroku
Oops!
Merge branch 'master' into heroku
ruby2.1.3
Added NewRelic
add librato-rails instrumentation