Remove dependency on FileUtils.

We now use our own implementation: RSpec::Support::DirectoryMaker
instead which implements mkdir_p for us.
Changelog entry for #1565

Conflicts:
	Changelog.md
Merge pull request #1565 from rspec/remove-fileutils

Remove fileutils
Prevent example groups named "Config" from generating a deprecation warning.
Merge pull request #1580 from jimmycuadra/avoid-config-warning

Prevent example groups named "Config" from generating a deprecation warning
changelog for #1580
Add an additional spec for the first from #1580.

The spec added in #1580 is a bit implicit in that
it depends upon RbConfig issuing a warning, which
may not always be the case in all versions of ruby.
The basic problem is that we were not ignoring top
level constants, so this added spec makes that
more explicit, and we can count on `Hash` always
being a top level constant even if RbConfig doesn’t
always issue the warning.
Merge pull request #1594 from rspec/add-extra-spec-for-1580

Add an additional spec for the first from #1580.
Use maintenance branch in the Gemfile.
Merge pull request #1597 from rspec/use-maint-branch-master

Use maintenance branch in the Gemfile.
3.0.1 release notes.

[ci skip]
Prefer CLI filter options to those in files
Merge pull request #1602 from trptcolin/filter_overriding

Prefer CLI filter options to those in files
Changelog for #1602.

[ci skip]
Fix misleading `:example_group` metadata deprecation warning.

Fixes #1562.
Merge pull request #1603 from rspec/fix-misleading-example-group-metadata-deprecation

Fix misleading `:example_group` metadata deprecation warning.
alternate implementation to #1602 that doesn't involve two conditionals per filter
Merge pull request #1605 from rspec/alternate_implementation_to_1602

Alternate 1602 implementation
Bump version to 3.1.0.pre to prevent confusion with master being 3.0.0 but 3.0.x releases are out.
remove redundant require statement