Implement `block.and` method
Use compile-time constants to simplify block size

Now the block typedef can be changed to any kind of uint and the rest of the
code will adjust itself to the new size.
Implement bitwise and with simple unit test
Add more unit tests and fix bugs in bitwise and
Additional unit tests for AND cases
Simplify AND code
Add a String() method on block for easier printing
Make bitArray.SetBit match sparseBitArray.SetBit
Debug `andSparseWithSparseBitArray()`

More comprehensive testing in the associated test as well (we're up to 100% over
the bitwise AND functions).
Add an And() method to the BitArray interface
Comments and docstrings on bitwise and
Rewrite andSparseWithDenseBitArray for less memory

Write an additional test case for a new edge case.
Rewrite andDenseWithDenseBitArray for efficiency

Improve unit test as well.
Fix accidentally-modified license
Fix accidentally-modified license in test file
Merge pull request #23 from Workiva/implement_bitwise_and

Implement bitwise and