Allow "#..." comments in .ctags

Allow the user to put comment lines in the `~/.ctags` file -- for example:

    # 'def[p] foo' method definitions in Elixir
    --regex-Elixir=/^[ \t]*def(p?)[ \t]+([a-zA-Z0-9_]+\.)*([a-zA-Z0-9_?!]+)/\3/d,definition/