v0.2.2

Prune the dead streaming fragments out of session logs, and the numbers for why.

Measured on a session that motivated this plugin: 272 MB on disk, 8.43 million objects on
load, 1.29 GB resident, out of memory. After a pass: 86.67 MB -> 16.99 MB, 169,795 fragments
gone, non-fragment content untouched (dropped=0).

What the file size costs on the read path (new in this release): 60 logs measured against
their own pre-cleanup copies -- 960,042 rows -> 300,868, 62,893 ms -> 6,668 ms across the set,
a median speedup of x7.77. The README states what that does NOT cover (projection computation
and client-side rendering were not measured).

Suite: 33 passed.