Check for Plack::Request, not just Plack.

Some of these tests were failing with an older Plack installed, which didn't
include Plack::Request.

This should resolve Issue 73 (at least by avoiding the test failures; whether we
actually need to declare a depedency on a newer Plack I don't know yet).

t/07_apphandlers/01_base.t

@@ -1,7 +1,7 @@
 use Test::More import => ['!pass'];
 
 plan skip_all => "Plack is needed for this test"
-    unless Dancer::ModuleLoader->load('Plack');
+    unless Dancer::ModuleLoader->load('Plack::Request');
 
 plan tests => 4;
 

t/07_apphandlers/02_apache2_plack.t

@@ -5,7 +5,7 @@ use warnings;
 use Test::More import => ['!pass'];
 
 plan skip_all => "Plack is needed for this test" 
-    unless Dancer::ModuleLoader->load('Plack');
+    unless Dancer::ModuleLoader->load('Plack::Request');
 
 plan tests => 2;
 

t/07_apphandlers/03_psgi_app.t

@@ -5,12 +5,14 @@ use Dancer::Config 'setting';
 use Dancer::ModuleLoader;
 
 plan skip_all => "Plack is needed to run this test"
-    unless Dancer::ModuleLoader->load('Plack::Loader');
+    unless Dancer::ModuleLoader->load('Plack::Request');
 plan skip_all => "LWP is needed to run this test"
     unless Dancer::ModuleLoader->load('LWP::UserAgent');
 plan skip_all => "Test::TCP is needed to run this test"
     unless Dancer::ModuleLoader->load('Test::TCP');
 
+Dancer::ModuleLoader->load('Plack::Loader');
+
 my $app = sub {
     my $env = shift;
     my $request = Dancer::Request->new($env);