update gemspec

mimemagic.gemspec

@@ -14,8 +14,10 @@ Gem::Specification.new do |s|
   s.require_paths = %w(lib)
 
   s.rubyforge_project = s.name
-  s.summary = 'Mime detection by extension or content'
+  s.summary = 'Fast mime detection by extension or content'
+  s.description = 'Fast mime detection by extension or content in pure ruby (Uses freedesktop.org.xml shared-mime-info database)'
   s.homepage = 'https://github.com/minad/mimemagic'
+  s.license = 'MIT'
 
   s.add_development_dependency('bacon')
   s.add_development_dependency('rake')