Fix for potential empty array in watched_keys
Don't use transactions (multi) for bitops

If you use a bitop against a frequently changing bitmap,
the multi can be cancelled because the underlying key tracked
by watch will change and invalidate the transaction.  The
biota will then return invalid results (0).  This removes the
transaction block.  Unknown if this is dangerous if the bitmap is
in the process of being copied.  Causes bitops to not be strongly
consistent.
Whitespace cleanup
Explicitly track chunk_keys as perf improvement

The chunk_keys method is frequently used and relies on Redis's
keys operator, which is costly for instances with large numbers
of keys.  This instead relies on a Redis set to track chunks,
and significantly improves performance.
Pipeline bit operations to increase speed.

In testing large bitmaps saw a ~50x increase in speed
by pipelining operations.
Merge branch 'whitespace'

* whitespace:
  Whitespace cleanup
Merge branch 'chunk_keys'

* chunk_keys:
  Explicitly track chunk_keys as perf improvement

Conflicts:
	lib/redis/bitops/sparse_bitmap.rb
Merge branch 'multi_fix'

* multi_fix:
  Pipeline bit operations to increase speed.
  Don't use transactions (multi) for bitops

Conflicts:
	lib/redis/bitops/sparse_bitmap.rb