Refactor is-even & belongs-to functions
Refactor is-even & belongs-to functions

- Closes #171

thoughtbot/neat,bahtiyara/neat,setie/neat,chriseppstein/neat,craftsmen/neat,greyhwndz/neat,Martskin/neat,thoughtbot/neat,smithdamen/neat,nickg33/neat,craftsmen/neat,jessieay/neat,bgreg/neat,thoughtbot/neat,kennethormandy/straight-up,2metres/neat,craftsmen/neat