Add rake task to reprocess sponsor logos

rake logo:reprocess

INSTALL.md

@@ -66,10 +66,9 @@ base operating systems. Check Google ;-)
 #### ImageMagick
 We use imagemagic for image manipulation of sponsor logo. You can get it from [direct install](http://software.opensuse.org/package/ImageMagick) page of the package or else check out [Download page](http://www.imagemagick.org/script/binary-releases.php) of ImageMagick.
 
-If you are upgrading your osem instance and would like to resize the exisiting logos, you would need to `reprocess!` the images:
+If you are upgrading your osem instance and would like to resize the exisiting logos, you would need to `reprocess!` the images. You can do it by running the following rake task:
 ```
-$ rails c
+$ rake logo:reprocess
-> Sponsor.find_each { |s| s.logo.reprocess! }
 ```
 
 #### Use openID

lib/tasks/logo.rake

@@ -0,0 +1,6 @@
+namespace :logo do
+  desc 'Resize existing logo of sponsors after change in image manipulation specifications'
+  task reprocess: :environment do
+    Sponsor.find_each { |s| s.logo.reprocess! }
+  end
+end