Update lib/rspec/core/example_group.rb

"action" alias for describe:

The purpose of this is to declare a description of some kind of action which is performed repeatedly on many sub-items with out "abusing" context and without needing to alias it_behaves_like and calling that repeatedly.

One situation where this would be useful would be an auditing database trigger that inserts a record into an auditing table for each column of the record that the trigger was fired on.

Currently it would be done something like this:
```rspec
describe "My Trigger" do
    context "When an update is done on a record" do
        it_performs "an audit", "COLUMN_ONE"
        it_performs "an audit", "COLUMN_TWO"
        it_performs "an audit", "COLUMN_THREE"
    end
end
```
Which outputs along the lines of:
```
My Trigger
    When an update is done on a record
        performs an audit
            On COLUMN_ONE
        performs an audit
            On COLUMN_TWO
        performs an audit
            On COLUMN_THREE
```
What the action alias would do is allow you to declare that a required action should take place, but to not repeat this for every item the action should happen for. Which would allow for the following:
```rspec
describe "My Trigger" do
    context "When an update is done on a record" do
        action "performs an audit" do
            include_examples "test the audit results", "COLUMN_ONE"
            include_examples "test the audit results", "COLUMN_TWO"
            include_examples "test the audit results", "COLUMN_THREE"
        end
    end
end
```
Which would output along the lines of:
```
My Trigger
    When an update is done on a record
        performs an audit
            On COLUMN_ONE
            On COLUMN_TWO
            On COLUMN_THREE
```
While there my be other benefits to this, the main purpose behind this idea is to enhance readability.