special id column helper
start of method missing impl
method missing accepts arg
repond_to_missing?
whatever
enforce arity in method missing
rename to subject for great flexibility
refactor into shared examples
refactor column definition methods into module for great sharing
the helpers should RETURN a column, not autoadd it
DERP
columns method now accepts columns to add
change a couple specs to use new column definition form
Merge pull request #4 from thejayvm/better-column-definition

Better column definition for visitors (Resolves #3)