Dependency on multi_json not declared properly

[agrimm]

If you have a small project, and you add logglier to your gemfile, you get

cannot load such file -- multi_json (LoadError)

This is because multi_json is listed as a development dependency in 189059a, not as a runtime dependency.

How to replicate:

• Create a fresh Rails project (4.2.1)
• Delete all gem requirements apart from logglier, rails, and sqlite3
• Run bundle rails c