Retainer

Retainer is used at run time in 5 crates. It's used only as a dev dependency in 1 crate.

Depender (with downloads and own rev deps)			Retainer version
120		rencfs		^0.3.0
		kapiti		^0.3
		force-rss		^0.3
		werkbank		^0.3.0
		fast42		^0.3
71K	2	ssh-agent-lib	dev	^0.3.0