make plugin work without session

[mtths]

currently, if sessions are disabled, the exception in Lexicon.pm line 64 gets rethrown [0]

please accept the patch below to make sessions optional

[0] Couldn't render template "core - Must specify session engine in settings prior to using 'session' keyword at /usr/local/share/perl/5.14.2/Dancer/Plugin/Lexicon.pm line 64.
" at /usr/local/share/perl/5.14.2/Dancer/Template/Abstract.pm line 89.

--- Dancer-Plugin-Lexicon-0.05-orig/lib/Dancer/Plugin/Lexicon.pm        2012-08-06 15:15:34.000000000 +0200
+++ Dancer-Plugin-Lexicon-0.05/lib/Dancer/Plugin/Lexicon.pm     2014-03-27 10:36:59.000000000 +0100
@@ -45,8 +45,10 @@
     my $settings = _setup_i18n();
     my $session_name = $settings->{session_name} || 'lang';

+    my $sessions_available = engine('session') ? 1 : 0;
+
     my $lang = param( $settings->{param_name} || "lang" )
-        || eval { session $session_name};
+        || ($sessions_available ? session($session_name) : undef);

     my @langs;
     if ($lang) {
@@ -61,7 +63,9 @@

     $lang = _set_language(@langs)->language_tag;

-    eval { session $session_name => $lang };
+    if ($sessions_available)  {
+        session $session_name => $lang ;
+    }
 };

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