Merge pull request #1350 from lfac-pt/master

Implements the _.property utility method
Use _.property in _.pluck
Merge pull request #1351 from caseywebdev/property-in-pluck

Use _.property in _.pluck
Use _.property in lookupIterator
Merge pull request #1352 from caseywebdev/property-in-lookup

Use _.property in lookupIterator
Implements the _. constant utility method

Higher-order identity function.

As proposed in #1345