Use type validations to check consistency

[pezholio]

Fixes #32 (I think)

As suggested by @ldodds. we're now using the TYPE_VALIDATIONS constant used for schemas to check cell formatting.

Currently checks for:

• Strings
• Integers
• URIs
• DateTimes
• Dates
• Times

This could possibly be improved by perhaps checking against common date / datetime formats and raise a warning if they don't match.

[coveralls]

Coverage remained the same when pulling 485352d on feature-32-improve-consistency-checks into c0ee948 on master.

[pezholio]

OK, so I've added Date / DateTime checking. Using ActiveSupport we now match against the date formats that ActiveSupport knows about and check they are mostly the same. If not, it raises an warning. We can also add date formats as per https://github.com/theodi/csvlint.rb/blob/feature-32-improve-consistency-checks/lib/csvlint/types.rb#L33