add support for object comparison

[ITProKyle]

Summary

Adds support to compare objects.

Why This Is Needed

An advantage to using troposphere is being able to unit test various iterations of a dynamic template. However, the lack of support for being able to compare objects with one another makes these test cumbersome to write.

Resolves #1821

What Changed

Added

• added .to_json() method to base classes
• added .__eq__() and .__ne__() methods to base classes
  • these use the newly added .to_json() method for comparison of same objects created from the same class to ensure properties are sorted in the same order
  • comparing against a dict (or list for AWSHelperFn to support Tags) uses .to_dict() instead of converting both to a JSON string
• added AWSHelperFn.__hash__()
  • tests/test_tags.py:TestTags.test_Unsortable was failing with TypeError: unhashable type: 'Sub' without it

[markpeek]

Thank you for adding this functionality.