refactory of tags for 'time', 'date' and 'datetime'
refactory of tags for 'time', 'date' and 'datetime'

- fxed input/view tag for 'time'
  - the time entered is the same time you get back from the db [#731]
  - the input-tag uses select_time
  - the view tag uses the canonical Time::DATE_FORMATS[:time]) and it is also overridable by just passing a strftime format as the format attribute
- the input tags are now a smart wrapper around select_date and select_time and accept all their options and any html option
- fixed the missing class attributes
- fixed an hidden bug: the input-tag for time was never called because ActiveSupport::TimeWithZone.name is 'Time' as Time.name
- updated doc

jpterry/hobo_fields,Invoca/hobo_fields,Invoca/hobo_fields