Add findByRecord and deprecate findById

[bmac]

Rename findById to findByRecord. Update all internal references of findById to findByRecord.

Add a new findById method that logs a deprecation warning then delegates to findByRecord.

[igorT]

emberjs/rfcs#27 (comment) calls it findRecord and not findByRecord ?

[HeroicEric]

@igorT I believe those are to be two separate methods (findByRecord and findRecord).

I asked @bmac about the differences earlier in slack and he said "findByRecord does some extra bookkeeping and should be private"

[igorT]

Ah is this just an internal cleanup?

[bmac]

Oops this should have been findRecord. My mistake