Add summary lines for `rbenv install` and `rbenv uninstall`

bin/rbenv-install

 #!/usr/bin/env bash
 #
+# Summary: Install a Ruby version using the ruby-build plugin
+#
 # Usage: rbenv install [-k|--keep] [-v|--verbose] <version>
 #        rbenv install [-k|--keep] [-v|--verbose] /path/to/definition
 #        rbenv install -l|--list
@@ -26,7 +28,7 @@ eval "$(ruby-build --lib)"
 
 usage() {
   # We can remove the sed fallback once rbenv 0.4.0 is widely available.
-  rbenv-help install 2>/dev/null || sed -ne '/^#/!q;s/.//;s/.//;1,2d;p' < "$0"
+  rbenv-help install 2>/dev/null || sed -ne '/^#/!q;s/.//;s/.//;1,4d;p' < "$0"
   [ -z "$1" ] || exit "$1"
 }
 

bin/rbenv-uninstall

 #!/usr/bin/env bash
 #
+# Summary: Uninstall a specific Ruby version
+#
 # Usage: rbenv uninstall [-f] <version>
 #
 #    -f  Attempt to remove the specified version without prompting
@@ -30,7 +32,7 @@ case "$DEFINITION" in
 "" | -* )
   # We can remove the sed fallback once rbenv 0.4.0 is widely available.
   { rbenv-help uninstall 2>/dev/null ||
-    sed -ne '/^#/!q;s/.\{1,2\}//;1,2d;p' < "$0"
+    sed -ne '/^#/!q;s/.\{1,2\}//;1,4d;p' < "$0"
   } >&2
   exit 1
   ;;