add rangeRing() for easier iteration

Change-Id: I0ef002c0c32c1435cbc62f954f98dc11c3f69945
ring docs

Change-Id: Ie26b98bb2e2946f326de6ff58677e33539db70b6
rename numberOf() to STL-like size()

Change-Id: I82332e91ed152e42b55ae921b3b61c5144253c39
test constness

Change-Id: I74523d0264f2fe78353c8f61d98295c65cd23ee1
simplify

Change-Id: I8cd66f270526880f6ad7fb083aaa65c87079dfc1