Remove spec= from Size usage in intro.rst.
Bump version in sphinx config from scripts/makebumpver.
Don't use integer division to calculate a fraction.
A Chunk is done growing when its pool is empty.
Honor the skip list when allocating leftover sectors.

The skip list was honored in the main share-based allocation loop, but
not in the secondary loop that allocates the leftovers.
Add some tests for Chunk and Request class hierarchy.