FLUME-2389. Spillable Memory Channel Example is incorrect

(Roshan Naik via Hari Shreedharan)
Updating RELEASE-NOTES for Flume 1.5.0.1
FLUME-2399. Update CHANGELOG for Flume 1.5.0.1
FLUME-2400. Dataset Sink is not built in hbase-98 profile
FLUME-2359. Update CHANGELOG to include FLUME-2400
FLUME-2399. Minor update to Release notes.