Fix bug where message params were not being trimmed properly

If you send a message that says:

    "!command foo bar "

(note the ending space) - the parameters given back to the plugin would
be:

    ["foo", "bar "]

which is kind of strange in this instance. Therefore, ending whitespace
is trimmed for parameters and trailing parameters.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

lib/irc/msg.ex

@@ -49,12 +49,13 @@ defmodule Omnibot.Irc.Msg do
 
     params =
       String.slice(params, 1..-1)
-      |> String.split(" ")
+      |> String.split()
       |> Enum.filter(fn s -> String.length(s) > 0 end)
 
     trailing =
       trailing
       |> String.slice(2..-1)
+      |> String.trim()
       |> Util.string_or_nil()
 
     params = if trailing, do: params ++ [trailing], else: params