Update workaround for "Outside the Scope of Strong Parameters" 

The previous example of how to permit a hash of unknown keys used .tap, but had the side effect of logging an "Unpermitted parameters" message despite being a successful workaround. The proposed workaround is ever so slightly better, imo, because it won't result in an "Unpermitted parameters" message being logged.
Fix undefined method error for NilClass

Add .try to prevent undefined method error for NilClass.
Removed unused require
Extract common database defaults; better use of YAML
Merge pull request #12292 from bf4/better_database_yaml

Extract common database defaults; better use of YAML
Merge pull request #12803 from arunagw/remove-unused-require

Removed unused require
Merge pull request #12609 from corwinkelly/patch-1

Update workaround for "Outside the Scope of Strong Parameters"
removes redundant curly brackets in example code [ci skip]
Don't skip tests if we don't need to.

We can conditional define the tests depending on the adapter or
connection.

Lets keep the skip for fail tests that need to be fixed.
Remove more skip
Mark broken test as pending

This will avoid the broken window effect in our test suite
:scissors: fix broken url [ci skip]
Start Running tests on Stable JRuby

Fixes for LOT of bugs have now landed in Jruby 1.7.6, thus we no longer
need to run tests against the master.

for broken tests that are still remaning:
1. If problem is in rails - we fix that test/code
2. if its a JRuby bug - we skip that test & file a bug report for jruby.
Merge pull request #12814 from gaurish/enable-jruby19-again

Start Running tests on Stable JRuby
Merge pull request #12813 from gaurish/patch-2

fix broken url/formatting in Asset pipeline guide [ci skip]