More minor translation/grammar fixes on error pages

app/views/errors/access_denied.html.haml

 .alert-message.block-message.error
   %h3 Access Denied
   %hr
-  %p Youre not allowed to access this page
+  %p You are not allowed to access this page.
   %p Read more about project permissions #{link_to "here", help_permissions_path, class: "vlink"}

app/views/errors/encoding.html.haml

@@ -2,5 +2,4 @@
   %h3 Encoding Error
   %hr
   %p
-    Page can't be loaded cause of encoding error
-
+    Page can't be loaded because of an encoding error.

app/views/errors/git_not_found.html.haml

@@ -6,4 +6,4 @@
     %span.label branch
     or
     %span.label commit
-    in your repository. Maybe it was moved
+    in your repository. It may have been moved.

app/views/errors/gitolite.html.haml

@@ -2,9 +2,6 @@
   %h3 Gitolite Error
   %h4 Application can't get access to your gitolite system.
 
-
-
-
 %h4 Tips for Administrator:
 
 %ul

app/views/errors/not_found.html.haml

 .alert-message.block-message.error
   %h3 Not found
   %hr
-  %p Resource you were looking for doesn't exist.
-  %P You may have mistyped the address or it was removed.
+  %p The resource you were looking for doesn't exist.
+  %p You may have mistyped the address or it may have been removed.