Bump to 0.4.0
Bump to 0.4.0

This release adds a cummulative moving average (cma) to the CKMS.
The cma is f64, implying that all types that CKMS can hold must
be able to be converted to f64. This is an API breaking change for
CKMS<u64 | usize | i64>.

Signed-off-by: Brian L. Troutwine <ccec23efb0a0e18dff61cc3fd9b4cf2532883527@postmates.com>

postmates/quantiles