[Fix] `nvm unload`: run `nvm deactivate` before unsetting everything.

Fixes #1399.
diff --git a/nvm.sh b/nvm.sh
index f02ffba..6b95788 100755
--- a/nvm.sh
+++ b/nvm.sh
@@ -3166,6 +3166,7 @@
       nvm_echo '0.33.0'
     ;;
     "unload" )
+      nvm deactivate >/dev/null 2>&1
       unset -f nvm \
         nvm_iojs_prefix nvm_node_prefix \
         nvm_add_iojs_prefix nvm_strip_iojs_prefix \