[Spec lib improvements] Prepend describe block names to spec names

[faultyserver]

This is part of a family of issues relating to Spec library improvements.

When defining specs within a describe block, it's common for those specs to have the describe blocks name prepended to their name in all places where the name of the spec is presented.

For example, with a spec suite like this:

describe "Some object" do
  it "does a thing" do
    assert(true == false)
  end
end

The error output should have the spec name "Some object does a thing".

Generally, this is done by having a Context object that holds onto the current name path at that point in the code. Entering a describe block would then push a new Context object to a stack, and each it block would then read the name path from the Context object at the top of that stack and prepend it to the given name for the spec when creating the SingleSpec instance.

An implementation like this should also work with nested describe blocks.

[faultyserver]

Implemented by #161.