Add usage to readme.
Add usage to readme.

wombatsecurity/karma-lolex-sinon-chai,FireVolkhov/karma-sinon-chai,janmonschke/karma-sinon-chai,keithamus/karma-chai,joemcbride/karma-sinon-chai,lucassus/karma-sinon-chai,xdissent/karma-chai,kmees/karma-sinon-chai,webdev1001/karma-sinon-chai,tubalmartin/karma-chai-sinon,jrrbru/karma-chai-sinon