Add `do` to the list of Elixir keywords

Added the `do` Elixir keyword to the list of Elixir keywords. For example when defining a function in Elixir:

  def sum(a, b) do
    a + b
  end

or when defining a module

  defmodule Mod do
    # stuff
  end
Merge pull request #60 from whatyouhide/patch-1

Add `do` to the list of Elixir keywords
Fix a problem with the `do` Elixir keyword

Before this commit, this use of the `do` keyword in Elixir would be
autocompleted with an `end` by vim-endwise:

  do
    # stuff
  end

But this would not:

  defmodule A do
    # no `end` here

By replacing a whitespace match (\s) with a wildcard (*) in the Elixir regex,
this now works.