Add metadata caching

Change-Id: Ic3fd0d353c66a8ae3732de7f6d342ed159f80b16
diff --git a/Makefile.PL b/Makefile.PL
index a2a43a7..8e659d4 100644
--- a/Makefile.PL
+++ b/Makefile.PL
@@ -11,26 +11,27 @@
   VERSION_FROM => 'lib/KorAP/XML/Krill.pm',
   LICENSE      => 'bsd_2',
   PREREQ_PM => {
-    'Mojolicious'    => 6.11,
-    'Packed::Array'  => 0.01,
-    'Log::Log4perl'  => 1.42,
-    'JSON::XS'       => 3.01,
-    'Set::Scalar'    => 1.26,
-    'XML::Fast'      => 0.11,
-    'Try::Tiny'      => 0.21,
-    'Array::IntSpan' => 2.003,
+    'Mojolicious'     => 6.11,
+    'Packed::Array'   => 0.01,
+    'Log::Log4perl'   => 1.42,
+    'JSON::XS'        => 3.01,
+    'Set::Scalar'     => 1.26,
+    'XML::Fast'       => 0.11,
+    'Try::Tiny'       => 0.21,
+    'Array::IntSpan'  => 2.003,
     'List::MoreUtils' => 0.33,
     'Parallel::ForkManager' => 1.17,
     'IO::Dir::Recursive' => 0.03,
-    'File::Temp'     => 0,
+    'File::Temp'      => 0,
     'Directory::Iterator' => 0,
-    'Benchmark'      => 0,
-    'Carp'           => 0,
-    'strict'         => 0,
-    'warnings'       => 0,
-    'utf8'           => 0,
-    'bytes'          => 0,
-    'Pod::Usage'     => 0
+    'Benchmark'       => 0,
+    'Carp'            => 0,
+    'strict'          => 0,
+    'warnings'        => 0,
+    'utf8'            => 0,
+    'bytes'           => 0,
+    'Pod::Usage'      => 0,
+    'Cache::FastMmap' => 1.40
   },
   MIN_PERL_VERSION => '5.014',
   test => {