Changed Application Layout to use Slim template

We used a gem called erb2slim to do the conversion.

Closes https://github.com/rapidftr/tracker/issues/130
Further small refactorings of Child model
rapidftr/tracker#106 Log error messages when API controller catches them
Merge pull request #666 from rdsubhas/master

Log error messages when API controller catches them
Merge pull request #659 from RapidRailsGirls/erb2slim

Merged, Thanks!