Modular style helper is available

ref https://github.com/padrino/padrino-framework/pull/1676

Add helper tests
Not '-' but '='

The behavior was changed in 0.12.0
ref
http://www.padrinorb.com/blog/padrino-0-12-0-activesupport-4-rewritten-reloader-smarter-rendering-and-loads-more
Not PADRINO_ENV but RACK_ENV

ref https://github.com/padrino/padrino-framework/pull/1445
Update to Padrino 0.12.2