Merge pull request #9426 from exviva/nested_attributes_reuse_existing_new_record

Do not overwrite manually built records during one-to-one nested attribute assignment
Conflicts:
	activerecord/CHANGELOG.md
Update Getting Started Guide - Strong Parameters [ci skip]
	modified:   guides/source/getting_started.md
Override Time.at to work with Time-like values

Time.at allows passing a single Time argument which is then converted
to an integer. The conversion code since 1.9.3r429 explicitly checks
for an instance of Time so we need to override it to allow DateTime
and ActiveSupport::TimeWithZone values.
Merge pull request #10710 from senny/5554_let_the_database_raise_on_counts

Remove column restrictions for `#count`, let the database raise if the SQL is invalid.
Conflicts:
	activerecord/CHANGELOG.md
Don't blindly call blame_file! on exceptions in ActiveSupport::Dependencies::Loadable

It is possible under some environments to receive an Exception that is
not extended with Blamable (e.g. JRuby).
ActiveSupport::Dependencies::Loadable#load_dependency blindly call
blame_file! on the exception which throws it's own NoMethodError
exception and hides the original Exception.

This commit fixes #9521