Minitest has already been required when calling Minitest.autorun.

Add `ActiveSupport::Testing::TimeHelpers#travel` and `#travel_to`. These
methods change current time to the given time or time difference by
stubbing `Time.now` and `Date.today` to return the time or date after
the difference calculation, or the time or date that got passed into the
method respectively. These methods also accept a block, which will
return current time back to its original state at the end of the block.

Example for `#travel`:

    Time.now # => 2013-11-09 15:34:49 -05:00
    travel 1.day
    Time.now # => 2013-11-10 15:34:49 -05:00
    Date.today # => Sun, 10 Nov 2013

Example for `#travel_to`:

    Time.now # => 2013-11-09 15:34:49 -05:00
    travel_to Time.new(2004, 11, 24, 01, 04, 44)
    Time.now # => 2004-11-24 01:04:44 -05:00
    Date.today # => Wed, 24 Nov 2004

Both of these methods also accept a block, which will return the current
time back to its original state at the end of the block:

    Time.now # => 2013-11-09 15:34:49 -05:00

    travel 1.day do
      User.create.created_at # => Sun, 10 Nov 2013 15:34:49 EST -05:00
    end

    travel_to Time.new(2004, 11, 24, 01, 04, 44) do
      User.create.created_at # => Wed, 24 Nov 2004 01:04:44 EST -05:00
    end

    Time.now # => 2013-11-09 15:34:49 -05:00

This module is included in `ActiveSupport::TestCase` automatically.

minitest/autorun required minitest/spec and we are avoiding to require
it.

https://github.com/seattlerb/minitest/commit/9a57c520ceac76abfe6105866f8548a94eb357b6#L15R8

+ Namespace changes, overhaul of runners.
+ Internal ivar name changes
- Removed a logger globally applied to tests that spew everywhere?!?
+ Override Minitest#__run to sort tests by name.
+ Reworked testing isolation to work with the new cleaner architecture.
- Removed a bunch of tests that just test minitest straight up. I think these changes were all merged to minitest 4 a long time ago.
- Minor report output differences.

Reason: on a second thought, minitest prints a seed as run option
regardless of the test order, and it actually calls srand, so
albeit it might be misleading I believe, it is the way it is and
should be left that way.

This reverts commit c15862ae.

See the first FIXME comment in the patch for the rationale.

This reverts commit 22bc12ec.

REASON: We will remove the MiniTest::Spec from Rails and we need these
methods again

Conflicts:
	activesupport/lib/active_support/test_case.rb

Sometimes, on Mac OS X, programmers accidentally press Option+Space
rather than just Space and don’t see the difference. The problem is
that Option+Space writes a non-breaking space (0XA0) rather than a
normal space (0x20).

This commit removes all the non-breaking spaces inadvertently
introduced in the comments of the code.

This reverts commit 1620df78, reversing
changes made to 2d000328.

Conflicts:
	activesupport/CHANGELOG.md
	activesupport/lib/active_support/test_case.rb

This only works with mocha v0.13.0 or later.

Note that this also fixes a few subtle bugs present in the current
implementation :-

* Mocha was raising a `MiniTest::Assertion` instead of a
  `Mocha::ExpectationError` as intended. The latter is not recognized by
  MiniTest as an assertion failure and so it is recorded as a test
  *error*, not a test *failure* as it ought to. This leads to
  potentially confusing output in the test results.

* Mocha verification should happen as part of the test. The verification
  of expectations is equivalent to a set of assertions. These assertions
  should happen as *part of* the test so that they have a chance to
  cause the test to fail, and not just as part of the teardown. Also if
  an assertion fails during the test, then there is no need to verify
  expectations, because only the first assertion failure is normally
  reported and all subsequent bets are off.

* Expectation verification should be counted as an assertion. Mocha
  cannot record each expectation verification as an assertion, because
  we weren't passing in an assertion counter to `#mocha_verify`.

It's sometimes hard to quickly find where deprecated call was performed, especially in case of migrating between Rails versions. So this is an attempt to improve the call stack part of the warning message by providing caller explicitly.

Fixing the build.

AS::TC::ConstantLookup walks the test's name to find the constant it is describing.
This additional lookup logic is needed to better support minitest's spec DSL.

minitest/spec provides `describe`, so deprecate the rails version and
have people use the superclass version

Remove rails implementation of describe, alias "test" to "it"