org: improve usage errors and add org ls filtering

lib/org.js

@@ -14,7 +14,7 @@ org.subcommands = ['set', 'rm', 'ls']
 org.usage =
   'npm org set orgname username [developer | admin | owner]\n' +
   'npm org rm orgname username\n' +
-  'npm org ls orgname'
+  'npm org ls orgname [<username>]'
 
 const OrgConfig = figgyPudding({
   json: {},
@@ -53,17 +53,27 @@ function org ([cmd, orgname, username, role], cb) {
       case 'rm':
         return orgRm(orgname, username, opts)
       case 'ls':
-        return orgList(orgname, opts)
+        return orgList(orgname, username, opts)
       default:
         UsageError()
     }
   }).then(
     x => cb(null, x),
-    err => err.code === 'EUSAGE' ? err.message : err
-  ).catch(cb)
+    err => cb(err.code === 'EUSAGE' ? err.message : err)
+  )
 }
 
 function orgSet (org, user, role, opts) {
+  role = role || 'developer'
+  if (!org) {
+    throw new Error('First argument `orgname` is required.')
+  }
+  if (!user) {
+    throw new Error('Second argument `username` is required.')
+  }
+  if (!['owner', 'admin', 'developer'].find(role)) {
+    throw new Error('Third argument `role` must be one of `owner`, `admin`, or `developer`, with `developer` being the default value if omitted.')
+  }
   return liborg.set(org, user, role, opts).then(memDeets => {
     if (opts.json) {
       output(JSON.stringify(memDeets, null, 2))
@@ -83,6 +93,12 @@ function orgSet (org, user, role, opts) {
 }
 
 function orgRm (org, user, opts) {
+  if (!org) {
+    throw new Error('First argument `orgname` is required.')
+  }
+  if (!user) {
+    throw new Error('Second argument `username` is required.')
+  }
   return liborg.rm(org, user, opts).then(() => {
     return liborg.ls(org, opts)
   }).then(roster => {
@@ -105,8 +121,18 @@ function orgRm (org, user, opts) {
   })
 }
 
-function orgList (org, opts) {
+function orgList (org, user, opts) {
+  if (!org) {
+    throw new Error('First argument `orgname` is required.')
+  }
   return liborg.ls(org, opts).then(roster => {
+    if (user) {
+      const newRoster = {}
+      if (roster[user]) {
+        newRoster[user] = roster[user]
+      }
+      roster = newRoster
+    }
     if (opts.json) {
       output(JSON.stringify(roster, null, 2))
     } else if (opts.parseable) {