Add Perltidy test in xt (related to #319)

- Add cpanfile, specifying dependencies for running the xt tests
  (authors tests, not installation tests)

cpanfile

@@ -0,0 +1,4 @@
+on 'develop' => sub {
+    requires 'Test::Fixme';
+    requires 'Test::PerlTidy';
+};

doc/dot.perltidyrc

@@ -6,7 +6,7 @@
 -cti=0 # No extra indentation for closing brackets
 -i=4   # Indent level is 4 cols
 -ci=4  # Continuation indent is 4 cols
--l=78  # Max line witdh is 78 cols
+-l=78  # Max line width is 78 cols
 -nolc  # Don't outdent long comments (* -olc)
 -nolq  # Don't outdent long quoted strings
 -nsbl  # No opening sub brace on new line (* -sbl)

xt/perltidy.t

@@ -0,0 +1,10 @@
+use strict;
+use warnings;
+
+use Test::PerlTidy;
+use FindBin qw($Bin);
+
+run_tests(
+    path       => "$Bin/../src/",
+    perltidyrc => "$Bin/../doc/dot.perltidyrc"
+);