Use Text::Diff instead of Text::WordDiff [minor]

Text::WordDiff has far more dependencies.  It's nicer, but probably not
worth the weight since it's only used for debugging output in
t/03-idempotency.t.

Author: Chris White

Makefile.PL

@@ -48,7 +48,7 @@ WriteMakefile(
         'Config' => '0',
         'File::Spec' => '0',
         'Text::ParseWords' => '0',
-        'Text::WordDiff' => '0',
+        'Text::Diff' => '0',   # for t/03-idempotency.t
     },
     PREREQ_PM => {
         'Getopt::Long'     => '2.5',    # Per issue #17

t/03-idempotency.t

@@ -2,7 +2,7 @@
 # Test running perlpp on itself - nothing should change.
 use rlib './lib';
 use PerlPPTest;
-use Text::WordDiff;
+use Text::Diff;
 use File::Spec;
 use Data::Dumper;
 plan tests => 1;
@@ -33,7 +33,7 @@ if($loaderr) {
 	run_perlpp $lrArgs, undef, \$out;
 
 	ok($out eq $wholefile, 'leaves its own source unchanged');
-	diag "Diff:\n" . word_diff \$wholefile, \$out unless $out eq $wholefile;
+	diag("Diff:\n" . diff \$wholefile, \$out) unless $out eq $wholefile;
 
 	#diag("Out:\n" . (@ARGV ? $out : substr($out,0,100)));
 	#diag("Wholefile:\n" . $wholefile) if @ARGV;