Make tests to look a bit better

This allows us to transform

describe("CONTEXT", function()
  it("DOES SOMETHING", function()
    -- do something
  end)
end)

into

describe "CONTEXT" (function()
  it "DOES SOMETHING" (function()
    -- do something
  end)
end)

which is easier to read (and write too, no comma :) )

Uses that Lua syntactic sugar:
  function("STR")  is equal to function "STR"
and a little bit of functional programming (anonymous funcs + closures)