fleshes out readme.md a little

README.md

@@ -3,9 +3,26 @@
 ## A Complete Mail Server Without Moving Parts
 
 ### Used Technologies
+ * nixos 16.03
+ * nixpkgs
  * dovecot
  * postfix
  * rmilter
  * rspamd
  * clamav
+ * opendkim
  * pam
+
+### Features
+ * unlimited domains
+ * unlimited mail accounts for every domain
+ * unlimited aliases for every mail account
+ * spam and virus checking
+ * dkim signing of outgoing emails
+
+### Nonfeatures
+ * moving parts
+ * SQL databases
+ * configurations that need to be made after `nixos-rebuild switch`
+ * complicated storage schemes
+ * webclients / http-servers