Added npm plugin.

plugins/npm/_npm

@@ -0,0 +1,19 @@
+#compdef npm
+
+# Node Package Manager 0.3.15 completion, letting npm do all the completion work
+
+_npm() {
+  compadd -- $(_npm_complete $words)
+}
+
+# We want to show all errors of any substance, but never the "npm (not )ok" one.
+# (Also doesn't consider "ERR! no match found" worth breaking the terminal for.)
+_npm_complete() {
+  local ask_npm
+  ask_npm=(npm completion --color false --loglevel error -- $@)
+  { _call_program npm $ask_npm 2>&1 >&3 \
+  | egrep -v '^(npm (not |)ok|ERR! no match found)$' >&2; \
+  } 3>&1
+}
+
+_npm "$@"