doc: merged old docs for Enumerable#inGroupsOf.
doc: merged old docs for Enumerable#inGroupsOf.

baiyanghese/prototype,Gargaj/prototype,erpframework/prototype,baiyanghese/prototype,292388900/prototype,ldf7801528/prototype,ShefronYudy/prototype,Jiasm/prototype,sstephenson/prototype,sdumitriu/prototype,fashionsun/prototype,loduis/prototype,erpframework/prototype,ldf7801528/prototype,sdumitriu/prototype,sstephenson/prototype,292388900/prototype,sdumitriu/prototype,lamsieuquay/prototype,loduis/prototype,lamsieuquay/prototype,ridixcr/prototype,fashionsun/prototype,fashionsun/prototype,loduis/prototype,erpframework/prototype,ridixcr/prototype,Jiasm/prototype,ShefronYudy/prototype,Jiasm/prototype,leafo/prototype,Gargaj/prototype,lamsieuquay/prototype,Gargaj/prototype,sstephenson/prototype,leafo/prototype,ldf7801528/prototype,ridixcr/prototype,292388900/prototype,ShefronYudy/prototype