Handles the sigil ~n
~n
Parses the number into a ComplexNum.
iex> ~n{1} ComplexNum.new(1) iex> ~n{0.1+12i} ComplexNum.new(0.1, 12) iex> ~n{0.1-0.12e-12i} ComplexNum.new(0.1, -0.12e-12) iex> ~n{1.1+3.12e-12i} ComplexNum.new(1.1, 3.12e-12)