Revert "better error for missing inverse on hasMany/belongsTo"

The commit was using Ember.isBlank which is still feature flagged.

This reverts commit f2ffe0715e6a778db05c65a501248a2d500100e5.
adapt usage example for TemperatureTransform

Adapt usage example to reflect the TemperatureTransform. 'raw' doesn't make sense here as it is not registered as such.
Merge pull request #2014 from jwahdatehagh/patch-1

adapt usage example for TemperatureTransform
Better error for missing inverse on hasMany/belongsTo
Merge pull request #2016 from emberjs/pr2012Cleanup

Better error for missing inverse on hasMany/belongsTo