fix wrong indentation on empty line between existing code

[tonini]

fixes #165

This fixes the problem of the wrong indentation when moving on a new empty line between existing code and the cursor get moved to the end of the line.

Examples:

defmodule Math do
    def max(list) do
                        # ...when you start typing
    Enum.reduce list, 0, fn(x, acc) ->
      if x > acc, do: x, else: acc
    end
  end
end

def generate_pkg(path, opts) do
  name = Path.basename(Path.expand(path))

  File.mkdir_p!(path)
                         # ...when you start typing
  File.cd! path, fn ->
    _generate_pkg(name, opts)
  end
end