* Closing #3066
 * Closing #3609

add grape-entity, that is split from grape 0.3.0.
remove usage of deprecated error_format, that is removed in grape 0.2.3.

In case we rescue from a fatal error, we want the error and the backtrace to
the error logged, so we can debug later on. This change injects the configured
logger from the rails app to the grape API and logs error as well as backtrace
in a rails-like fashion.

This rescues all errors and returns a proper JSON response. Fixes #2833.

  * fixed in grape v0.2.2

Merge branch 'master' into non-interactive-aws-install

Conflicts:
	doc/installation.md

Fix merge mess in installation.md

Didn't bother with files in db/, config/, or features/