Add missing theme screenshots

modules/prompt/functions/prompt_minimal_setup

@@ -5,6 +5,9 @@
 #   Brian Tse <briankftse@gmail.com>
 #   Sorin Ionescu <sorin.ionescu@gmail.com>
 #
+# Screenshots:
+#   http://i.imgur.com/zLZNK.png
+#
 
 function +vi-git-status() {
   # Check for untracked files or updated submodules since vcs_info does not.

modules/prompt/functions/prompt_nicoulaj_setup

@@ -15,6 +15,9 @@
 #   - Shows user@hostname if connected through SSH.
 #   - Shows if logged in as root or not.
 #
+# Screenshots:
+#   http://i.imgur.com/Xe1bu.png
+#
 
 function prompt_nicoulaj_precmd {
   vcs_info

modules/prompt/functions/prompt_steeef_setup

@@ -8,6 +8,9 @@
 #   steeef <steeef@gmail.com>
 #   Sorin Ionescu <sorin.ionescu@gmail.com>
 #
+# Screenshots:
+#   http://i.imgur.com/HyRvv.png
+#
 
 function virtualenv_info {
   if [[ -n "$VIRTUAL_ENV" ]]; then