Add helper functions for bitwise operations.

Relates #26.
Document preconditions.
Replace bitmap transposition with print.

The tranpose algorithm did not scale beyond small toy examples because it kept
the entire transposed bitstream matrix in memory. The new replacement algorithm
can transpose an arbitrary bitstream through its basic iterator (which goes
over all 1s).
Implement random access and point-based EWAH find.

This commit makes the EWAH bitstream implementation feature-complete. We now
support now random access of any bits and forward/backward search from a given
point. The time complexity of these operations is O(b) where b represents the
number of blocks.

Relates #26.