Use Text::Whitespace token in Console lexer (#894)

The Console lexer uses the `Text` token for the whitespace between the
console prompt character and the text that begins the command on a
particular line. Using `Text::Whitespace` is more expressive and allows
users to do things like define CSS rules that disable selection.

lib/rouge/lexers/console.rb

@@ -116,7 +116,7 @@ def process_line(input, &output)
           # before we pass to the lang lexer so it can determine where
           # the "real" beginning of the line is
           $' =~ /\A\s*/
-          yield Text, $& unless $&.empty?
+          yield Text::Whitespace, $& unless $&.empty?
 
           lang_lexer.continue_lex($', &output)
         elsif comment_regex =~ input[0].strip