deep interpolation

[fl00r]

Sometimes I need to get a key with a bunch of inner keys and I can't get them interpolated.

people:
  ann: 'Ann is %{ann}'
  john: 'Ann is %{john}'

I18n.t 'people', ann: 'good', john: 'big'
#=> { ann: 'Ann is %{ann}', john: 'John is %{john}' }

# Proposing this approach
I18n.t 'people', ann: 'good', john: 'big', deep_interpolation: true
#=> { ann: 'Ann is good', john: 'John is big' }

[radar]

This looks good to me and I would like to include it in the 0.8.0 release. @fl00r could you please update this branch against master?

[fl00r]

:D

joke about 2 years anniversary

Done

[radar]

Thank you @fl00r!