Don't swallow exceptions in transctional statements

The MySQL connection adapater swallows all StandardError exceptions,
which includes Mysql::Error and Mysql2::Error. The comment in the
exception clause claims errors thrown here indicate that transactions
aren't supported by the server but that isn't necessarily true. It's
possible the MySQL server has gone away and swallowing a failed commit
may let the application return a successful response when the data has
not been saved. Also, replication libraries like Galera require that the
application handle exceptions thrown at BEGIN/COMMIT.

I'm unable to determine what version of MySQL threw an exception for
transactional statements. I tried as far back as 3.23.49 with InnoDB
disabled but BEGIN & COMMIT statements do not throw an error. If there's
a real case for this logic to continue, we could instead push this
behavior into a configuration setting.

The exception swallowing has been there since the beginning:
db045dbbf60b53dbe013ef25554fd013baf88134
Explicitly exit with status "1" for create and drop failures

* A non-zero exit status allows subsequent shell commands to be chained
  together such as: `rake db:reset test:prepare && rspec && cap deploy`
  (if you're feeling brave :)
* Any exceptions raised during the `create` and `drop` tasks are caught
  in order to print a "pretty" message to the user. Unfortunately doing
  so prevents rake from aborting with a non-zero exit status to the shell.
* Therefore we re-raise the exceptions after the "pretty" message and
  re-catch them in the task.
* From the task we explicitly exit with a non-zero status. This method
  was chosen (rather than just letting rake fail from the exception) so
  that the backtrace is suppressed and the output to stderr is
  unchanged.
* Update activerecord CHANGELOG
Set branch for arel in Gemfile so that we can use bundle local config [ci skip]
Fix AR Changelog examples and improve syntax highlight [ci skip]
Fix test name [ci skip]
Avoid creation of extra hash with merge just to set a value
Simplify number parsing logic in numericality validation
Use a simple conditional rather than short circuit with next
Avoid a new hash allocation
Make code simpler to read by using a case statement
Cache regexp source on format validation to avoid allocating new objects

Example:

    >> r = /some-regexp/
    => /some-regexp/
    >> r.source.object_id == r.source.object_id
    => false
Remove argument that is accessible as attribute
Only check that the option exists once instead of doing on each conditional
Invert conditional to avoid double checking for Regexp
Remove short circuit return in favor of simple conditional
Allocate one less object using html_safe during content_tag construction
document id prefixed String usage of `.find`. refs #12891 [ci skip]
Take Hash with options inside Array in #url_for
Merge pull request #9599 from ognevsky/hash-inside-array-in-url-for

Take Hash with options inside Array in #url_for
Fix CHANGELOG typo [ci skip]