Fix names with spaces in letter-avatars

Seems like there is a possible problem when a name containing a space is
passed to this function. using urlencode on the name should fix possible
problems here.

Signed-off-by: Sheogorath <sheogorath@shivering-isles.com>

lib/letter-avatars.js

@@ -30,6 +30,7 @@ exports.generateAvatarURL = function (name, email = '', big = true) {
   if (typeof email !== 'string') {
     email = '' + name + '@example.com'
   }
+  name=encodeURIComponent(name)
 
   let hash = crypto.createHash('md5')
   hash.update(email.toLowerCase())