[#1] Fix sparse => shallow naming throughout.

For some reason best known to a former self of mine, I named the very
first strategy implemented 'sparse' when it is in fact 'shallow'.
Rename all mentions of sparse to shallow throughout.

A strategy by any other name would confuse as sweet.
Bump version to v0.2.0 , updating CHANGELOG.
Merge branch 'release/v0.2.0' into stable