Fix usage of value in multi count

Make uniqueness check more robust

This doesn't just fail if the unique value already exists, but also
checks to see if it's different than the value currently being indexed.

Fix current_values not being written out

Add conditional indexing

Also now rebuilds the current_values on each index run, which ensures
current values that are being used are stored.

Prepped 2.2.0

Prep 2.0.0 release

Add special handling for interrogative methods

Fix double #deindex_by_primary_key

When there was a multi index, deindexing twice would cause an invalid
watch.

Add .deindex_by_primary_key!

Bumps the version to 1.4.0.
Notes the usage of the MIT license.

Prep 1.2.1