[ADD] Filtering XMPP commands

This allows us to have commands apply to admins or MUCs only(which would
help with many things I want to implement).

README.MD

@@ -55,7 +55,8 @@ parsee-config \
     -H 'blow.hole' \ # Matrix homeserver name
     -J 'parsee.blow.hole' \ # XMPP component host, must be reachable
     -s 'A very secure XMPP component secret' \
-    -p 5347
+    -p 5347 \
+    -M 65535 # Maximum stanza size. Stanzas larger than this from Parsee will be dropped to avoid stream closures. Leave this empty if you're unsure.
 ```
 
 If everything goes well, it should generate a `parsee.json` file.
@@ -72,7 +73,12 @@ Currently, the main sources of documentation are the Ayadocs(for headers) and th
 
 ## TODOS before 1.0 rolls around
 - Make Parsee actually go *vroooooooooommmmmmm*.
+- Make sure Parsee can easily run on just about any reasonable POSIX 
+system.
 - Avoid making 'back-puppets' from Matrix as much as possible
+- Extension support. I'd need to design a good system, and maybe do it 
+with either shared libraries(`dlopen`/`dlclose` on POSIX) or use a 
+language like Janet or Lua.
 - Add [libomemo](https://github.com/gkdr/libomemo) or something as an optional dependency. 
     - It depends on more stuff anyways, and I don't want to weigh down the 
     dependency list of Parsee for that.