Cleanup: Move common functionality to a base class

- Enhancement: Add a base class for Valere Client tests so that we can capture all the httpretty required functionality in one place
  - Sub-classes can implement a small function in the tests that can then call the appropriate base-class function for the multi-call support
  - Updated existsing Valere Client tests to use the new base class
Cleanup: Moved basic httpretty callback functionality to base class

- Moved the functionality to base class, making the in-test callback a simple wrapper
  - This allows other tests to be able to use the same functionality with ease
Cleanup: Code Logic Reduction

- Added two functions for calculating the positional data in the storage and metadata block lists
  - Updated all functionality that calculated a position in the list to use the new functions
Bug Fix: Corrected function names

- The "body" generators were not really for the listing body; updated names for a little better self-documentation
Refactor: Build deuceclient.api.Block data

- For building more extensive API emulation we need to track all the data
Check Point: Rafactor, Bug Fixes, etc

- Use version of HTTPretty that has a couple Python3 fixes applied until a new version with the fixes is released
  - PR https://github.com/gabrielfalcao/HTTPretty/pull/193 resolved a major issue with the tests running
  - My own PR https://github.com/gabrielfalcao/HTTPretty/pull/201 makes the decorator cleaner and more well behaved
- Refactored functionality in deucevalere/tests/client_base.py in prep for being able to HEAD a block
- Made the log a part of the class instead of having to rebuild access to it in each function
Enhancement: Testing of Block Validation

- Adds unit tests for the block validation functionality
- Corrects some bugs in the block validation functionality
Enhancement: Testing of Block Cleanups

- Adds testing for the cleanup of blocks that were found to have been expired
- Refactor: We needed a try/except around the block deletion call