Example.rb: Remove key type (ssh-rsa) from keys

The key type portion of a `known_hosts` line (`ssh-rsa` or similar)
duplicates information already present in the Base 64 encoded string
containing the key itself. Thus there's no need for our `KnownHosts`
class to require anything but the Base 64 portion of the key. The type
was actually ignored, anyway, except for being stripped off before the
Base 64 string was decoded and passed to the `Net::SSH::Buffer` class.

Thus, we remove this to avoid both unnecessary code and confusion.

It's not clear where the idea of prefixing the line with the key type
and stripping it off came from; the equivalant code from Net::SSH
(`KnownHosts.keys_for()`) has since at least 2.9.4 done a (more
proper) parse of SSH `known_hosts` file format with the host
names/addresses in front of the key type. Probably when I implemented
my version I just dropped the host names without really thinking about
what was going on.

(`Net::SSH::KnownHosts` class does also check the key type from
outside the Base 64 encoded portion of the `known_hosts` line, but
it's not clear how useful this really is since it seems just to guess
what formats will be known by `Buffer.read_key`.)

Example.rb

@@ -84,8 +84,11 @@
 # with a key that we know.
 #
 host = 'github.com'
-hostkey = 'ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAq2A7hRGmdnm9tUDbO9IDSwBK6TbQa+PXYPCPy6rbTrTtw7PHkccKrpp0yVhp5HdEIcKr6pLlVDBfOLX9QUsyCOV0wzfjIJNlGEYsdlLJizHhbn2mUjvSAHQqZETYP81eFzLQNnPHt4EVVUh7VfDESU84KezmD5QlWpXLmvU31/yMf+Se8xhHTvKSCZIFImWwoG6mbUoWf9nzpIoaSjB+weqqUUmpaaasXVal72J+UX2B+2RPW3RcT0eOzQgqlJL3RKrTJvdsjE3JEAvGq3lGHSZXy28G3skua2SmVi/w4yCE6gbODqnTWlg7+wC604ydGXA8VJiS5ap43JXiUFFAaQ=='
-wronghostkey = 'ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC1VJn8gp5A8FZRpemLgUePg/qlsJWqZYxVMtjOvziCh/vKXoCuddWo8Ehsxm++1fwMIf0BIZXQpH1EymH8joMOImfDm8UQ5OsTnP5T5+9NF7dH6BveK8VIZTJcRGX80CzfpEESmC0I3fbB1JoMVwEvznQnSveIcfvyhhoGUIO1L3L06s2LBRQRuGpM3razYW0W0z9qXegEivxQpvjG5OLAkaoVtdZ5zMlkGbKf+IWXL9S0pCZWrtOBLG42m5UF5V3vTfi2+Fiq8pMhGlMcpsgJ3bzuf93m+v7Z+bGbsI+Qq2qsT8cm7j8YH9TaUq9A737yPQeSuGpTovq5c6rqmo/D'
+
+# These are "ssh-rsa" keys; it appears that 'Net::SSH' can figure this
+# out automatically (and presumably other types as well).
+hostkey = 'AAAAB3NzaC1yc2EAAAABIwAAAQEAq2A7hRGmdnm9tUDbO9IDSwBK6TbQa+PXYPCPy6rbTrTtw7PHkccKrpp0yVhp5HdEIcKr6pLlVDBfOLX9QUsyCOV0wzfjIJNlGEYsdlLJizHhbn2mUjvSAHQqZETYP81eFzLQNnPHt4EVVUh7VfDESU84KezmD5QlWpXLmvU31/yMf+Se8xhHTvKSCZIFImWwoG6mbUoWf9nzpIoaSjB+weqqUUmpaaasXVal72J+UX2B+2RPW3RcT0eOzQgqlJL3RKrTJvdsjE3JEAvGq3lGHSZXy28G3skua2SmVi/w4yCE6gbODqnTWlg7+wC604ydGXA8VJiS5ap43JXiUFFAaQ=='
+wronghostkey = 'AAAAB3NzaC1yc2EAAAADAQABAAABAQC1VJn8gp5A8FZRpemLgUePg/qlsJWqZYxVMtjOvziCh/vKXoCuddWo8Ehsxm++1fwMIf0BIZXQpH1EymH8joMOImfDm8UQ5OsTnP5T5+9NF7dH6BveK8VIZTJcRGX80CzfpEESmC0I3fbB1JoMVwEvznQnSveIcfvyhhoGUIO1L3L06s2LBRQRuGpM3razYW0W0z9qXegEivxQpvjG5OLAkaoVtdZ5zMlkGbKf+IWXL9S0pCZWrtOBLG42m5UF5V3vTfi2+Fiq8pMhGlMcpsgJ3bzuf93m+v7Z+bGbsI+Qq2qsT8cm7j8YH9TaUq9A737yPQeSuGpTovq5c6rqmo/D'
 
 puts("You should see no exceptions.")
 
@@ -146,12 +149,12 @@ def search_for(host, options = {})
 
     attr_reader :host
 
-    def initialize(host, pubkeys)
+    def initialize(host, base64_pubkeys)
         @host = host
-        super(pubkeys.map { |keyline|
-            type, key = keyline.split(' ', 2)
-            # XXX we just assume it's a supported type, yeah, that's lazybad
-            blob = key.unpack('m0*').first
+        super(base64_pubkeys.map { |base64key|
+            # The type is encoded in the key information; we let
+            # `read_key` determine whether it likes it or not.
+            blob = base64key.unpack('m0*').first
             Net::SSH::Buffer.new(blob).read_key
         })
     end