Example: Don't include internal root group in name

Due to an internal implementation detail, all examples belong to an
example group. When not explicitly added to an example group, Quick adds
examples to an internal "root example group". This is to handle cases
like:

    override func spec() {
      beforeEach { /* ... */ }
      it("is an example") { /* ... */ }
    }

`beforeEach` closures need to be executed within an example group, so in
the above case Quick adds the example to an internal group.

This internal group, however, appears in example names. The above
example name was reported as "root example group, is an example". This
obviously isn't the intended example name, and the bug was reported in
issue #168.

In order to fix the issue, add a flag to example groups to determine
whether they are internal root example groups. If they are, do not
return a name.
QuickSpec: Remove unused class declaration
World: Move singleton methods into extension
DSL: Move DSL onto World extension

The Swift DSL class functioned as a container for a group
of class methods. This means that an instance of DSL could
be instantiated using `DSL()`--something that made no
conceptual sense.

Instead, move DSL methods onto a category on World. Also:

- Move DSL-related files into a DSL directory.
- Add documentation to all Swift DSL, and some Objective-C DSL.
NSString+QCKSelectorName: Add documentation
DSL: Delete unused DSL.swift

Quick/DSL.swift was removed from the Xcode project file in
e32aa85a6be130a7deca54f02460d18a4480f443.
Quick.xcodeproj: Remove file from old workspace

Quick-iOS.xcscheme belonged to the Quick.xcodeproj that was removed in
4a6f7d514c69e2fc9786261e80080af151f747e9.
Add example and suite hooks

Add hook objects as containers for beforeEach/afterEach and
beforeSuite/afterSuite. Quick will soon be configurable to execute
suite-wide beforeEach/afterEach closures--this makes that change easier.

This commit also introduces typealiases for each of the hook closure
types, and uses them throughout the codebase.
Rename OSX targets and scheme.
Merge branch 'paulyoung-rename-osx-targets-scheme'