Add `rails test` command to run the test suite

To run the whole test suite:

    $ rails test

To run the test file(s):

    $ rails test test/unit/foo_test.rb [test/unit/bar_test.rb ...]

To run the test suite

    $ rails test [models,helpers,units,controllers,mailers,...]

For more information, see `rails test --help`.

This command will eventually replacing `rake test:*`, and `rake test`
command will actually invoking `rails test` instead.
Update testing documentation

* Update test invocation to use `rails test` instead.
* Update all the test command previews (since we're now using MiniTest.)
* Mentioning MiniTest instead of Test::Unit.
* Update list of test suites.
Add support for MiniTest flags in TestRunner

Any flags that got set will be passed through to MiniTest::Unit.runner,
such as `-n`, `-s-, and `-v`.
Load fixtures only when running suites, or `-f`

* `rails test -f` will run the test suites with all fixtures loaded
* New application will now generated without `fixtures :all` line
  enabled by default.
Improve wording for rails test command
Change uniq validation with conditions examples to use where with hashes

Take the opportunity to showcase where.not.
Update Rake tasks to call `rails test` instead

Also, print out deprecation warning for other rake tasks except
`rake test` and `rake` (default)
Make sure that `rails test` load test in test env
Make sure that debugger isn't included in production environment.
Merge pull request #9638 from siong1987/debugger

Make sure that debugger isn't included in production environment.
document habtm join-table name with custom prefix [ci skip].

Closes #9643.

The logic was introduced with 46492949
Merge pull request #9645 from senny/9643_habtm_wrong_table_name

document habtm join-table name with custom prefix [ci skip]
Address ActiveRecord::StatementInvalid: OCIError: ORA-00979
Change from each to each_value on hash to avoid unused variable warning
Merge pull request #9650 from yahonda/group_by_oracle

Address ActiveRecord::StatementInvalid: OCIError: ORA-00979
Merge pull request #9651 from vipulnsward/change_to_each_value_intest

Change from each to each_value on hash to avoid unused variable warning
Fixed tests for returning an instance of `Time` in the local system timezone.
Merge pull request #9653 from jetthoughts/master

Fixed tests `to_time` returning an instance of `Time` in the local system timezone.

Tests for to_time returning an instance of Time in the local system timezone did not take in account DST when they used mixed timezone declarations like 'US/Eastern' and '-0500'.

Replaced timezone with DST by timezone without DST.
Cleanup tests for unused variables
add an missing assertion to inheritance_test.rb

assertion for
https://github.com/rails/rails/blob/ad624345e54bd20802de67b2b5c9ef29ecf5
d5f4/activerecord/lib/active_record/inheritance.rb#L32