Copy changed_attributes across to newly become'd records

Without this, the original record's values won't get saved, since the partial insertions support (https://github.com/rails/rails/commit/144e8691cbfb8bba77f18cfe68d5e7fd48887f5e) checks for changed values and thinks there are none.
Update to Unicode 6.3.0

6.3.0 was released on September 30, 2013.

http://unicode-inc.blogspot.com.ar/2013/09/announcing-unicode-standard-version-63.html
Merge pull request #13474 from jdelStrother/becomes

Copy changed_attributes across to newly become'd records
Merge branch 'master' of github.com:rails/rails
Typo fix [ci skip]
Merge pull request #13513 from ilja/master

Typo fix [ci skip]
setting `changed_attributes` instance variable if it is already initialized.
Merge pull request #13514 from kuldeepaggarwal/f-removed-warnings

Removed warnings: setting `changed_attributes` instance variable if it is already initialized.
Extracted blank matcher regexp to constant
Merge pull request #13517 from jetthoughts/13516_blank_to_return_true_false

String#blank? returns True/False
blank? and present? commit to return singletons [Xavier Noria & Pavel Pravosud]

The contract of blank? and present? was in principle to return Object, as we
generally do, the test suite and description was consistent with that, but some
examples had comments like "# => true".

This cannot be unclear, we either fix the examples, or update the contract.

Since users may be already assuming singletons due to the examples and the fact
that they were returned before 30ba7ee, the safest option seems to be to revise
the contract and the implementation of String#blank?

The motivation for 30ba7ee was to improve the performance of the predicate, the
refactor based on === is on par regarding speed.

With this commit we start documenting return types using YARD conventions. We
plan to document return types gradually.