make warnings more obvious

This changes the output from:

```
-----> Writing config/database.yml to read from DATABASE_URL
-----> Preparing app for Rails asset pipeline
       Running: rake assets:precompile
       DEPRECATION WARNING: Model based mass assignment security has been extracted
       out of Rails into a gem. Please use the new recommended protection model for
       params or add `protected_attributes` to your Gemfile to use the old one.
       To disable this message remove the `whitelist_attributes` option from your
       `config/application.rb` file and any `mass_assignment_sanitizer` options
       from your `config/environments/*.rb` files.
       See http://guides.rubyonrails.org/security.html#mass-assignment for more information.

       I, [2014-07-07T20:35:13.178958 #972]  INFO -- : Writing /tmp/build_302f5b43-de60-418f-8002-8169aa9b0201/public/assets/rails-1a1ca78f5753b7fe0e44812de505bf4d.png
       I, [2014-07-07T20:35:13.253829 #972]  INFO -- : Writing /tmp/build_302f5b43-de60-418f-8002-8169aa9b0201/public/assets/application-c55d0fe07cdfb00787af6d2822ed29a9.js
       I, [2014-07-07T20:35:13.318124 #972]  INFO -- : Writing /tmp/build_302f5b43-de60-418f-8002-8169aa9b0201/public/assets/application-58c7c0e35a67f189e19b8c485930e614.css
       Asset precompilation completed (1.95s)
       Cleaning assets
       Running: rake assets:clean
       DEPRECATION WARNING: Model based mass assignment security has been extracted
       out of Rails into a gem. Please use the new recommended protection model for
       params or add `protected_attributes` to your Gemfile to use the old one.
       To disable this message remove the `whitelist_attributes` option from your
       `config/application.rb` file and any `mass_assignment_sanitizer` options
       from your `config/environments/*.rb` files.
       See http://guides.rubyonrails.org/security.html#mass-assignment for more information.

-----> WARNINGS:
       Include 'rails_12factor' gem to enable all platform features
       See https://devcenter.heroku.com/articles/rails-integration-gems for more information.
       
       You have not declared a Ruby version in your Gemfile.
       To set your Ruby version add this line to your Gemfile:
       ruby '2.0.0'
       # See https://devcenter.heroku.com/articles/ruby-versions for more information.

       No Procfile detected, using the default web server (webrick)
       https://devcenter.heroku.com/articles/ruby-default-web-server
-----> Discovering process types
       Procfile declares types -> (none)
       Default types for Ruby  -> console, rake, web, worker

-----> Compressing... done, 20.3MB
-----> Launching... done, v8
       http://test-app-1404765275-9889977.herokuapp.com/ deployed to Heroku
```

to this which I feel is more commanding:

```
-----> Writing config/database.yml to read from DATABASE_URL
-----> Preparing app for Rails asset pipeline
       Running: rake assets:precompile
       DEPRECATION WARNING: Model based mass assignment security has been extracted
       out of Rails into a gem. Please use the new recommended protection model for
       params or add `protected_attributes` to your Gemfile to use the old one.
       To disable this message remove the `whitelist_attributes` option from your
       `config/application.rb` file and any `mass_assignment_sanitizer` options
       from your `config/environments/*.rb` files.
       See http://guides.rubyonrails.org/security.html#mass-assignment for more information.

       I, [2014-07-07T20:35:13.178958 #972]  INFO -- : Writing /tmp/build_302f5b43-de60-418f-8002-8169aa9b0201/public/assets/rails-1a1ca78f5753b7fe0e44812de505bf4d.png
       I, [2014-07-07T20:35:13.253829 #972]  INFO -- : Writing /tmp/build_302f5b43-de60-418f-8002-8169aa9b0201/public/assets/application-c55d0fe07cdfb00787af6d2822ed29a9.js
       I, [2014-07-07T20:35:13.318124 #972]  INFO -- : Writing /tmp/build_302f5b43-de60-418f-8002-8169aa9b0201/public/assets/application-58c7c0e35a67f189e19b8c485930e614.css
       Asset precompilation completed (1.95s)
       Cleaning assets
       Running: rake assets:clean
       DEPRECATION WARNING: Model based mass assignment security has been extracted
       out of Rails into a gem. Please use the new recommended protection model for
       params or add `protected_attributes` to your Gemfile to use the old one.
       To disable this message remove the `whitelist_attributes` option from your
       `config/application.rb` file and any `mass_assignment_sanitizer` options
       from your `config/environments/*.rb` files.
       See http://guides.rubyonrails.org/security.html#mass-assignment for more information.

###### WARNING:
       Include 'rails_12factor' gem to enable all platform features
       See https://devcenter.heroku.com/articles/rails-integration-gems for more information.

###### WARNING:
       You have not declared a Ruby version in your Gemfile.
       To set your Ruby version add this line to your Gemfile:
       ruby '2.0.0'
       # See https://devcenter.heroku.com/articles/ruby-versions for more information.

###### WARNING:
       No Procfile detected, using the default web server (webrick)
       https://devcenter.heroku.com/articles/ruby-default-web-server

-----> Discovering process types
       Procfile declares types -> (none)
       Default types for Ruby  -> console, rake, web, worker

-----> Compressing... done, 20.3MB
-----> Launching... done, v8
       http://test-app-1404765275-9889977.herokuapp.com/ deployed to Heroku
```