Created a new PyPI package release 1.3.1.
Added instructions for creating a PyPI package release.
Filled out documentation stubs for .if_length_equals(), etc., operators.
Corrected errors in previous commit of documentation changes.
Added tests for .if_length_equals() operator in test1.
Added the .if_length_equals(), .if_length_less_than(), and .if_length_more_than() operators.