Misc updates to babel-core README (#5841) [skip ci]
Misc updates to babel-core README (#5841) [skip ci]

* Minor grammar things
* Standardize fullstops on the options table
* Usage of `` where appropriate
kaicataldo/babel,hzoo/babel,chicoxyzzy/babel,samwgoldman/babel,babel/babel,hulkish/babel,vadzim/babel,babel/babel,hzoo/babel,samwgoldman/babel,kellyselden/babel,chicoxyzzy/babel,jridgewell/babel,existentialism/babel,maurobringolf/babel,kedromelon/babel,chicoxyzzy/babel,claudiopro/babel,hzoo/babel,jridgewell/babel,kellyselden/babel,maurobringolf/babel,kaicataldo/babel,claudiopro/babel,hulkish/babel,existentialism/babel,kaicataldo/babel,babel/babel,samwgoldman/babel,jridgewell/babel,PolymerLabs/babel,Skillupco/babel,kellyselden/babel,babel/babel,kedromelon/babel,shuhei/babel,shuhei/babel,vadzim/babel,kellyselden/babel,maurobringolf/babel,kedromelon/babel,hzoo/babel,guybedford/babel,guybedford/babel,hulkish/babel,Skillupco/babel,chicoxyzzy/babel,Skillupco/babel,kaicataldo/babel,hulkish/babel,jridgewell/babel,Skillupco/babel,shuhei/babel,claudiopro/babel,guybedford/babel,existentialism/babel,PolymerLabs/babel,PolymerLabs/babel