Add initial support for composer plugins (#59)

* Add support for composer plugins

* Permit omitting any component of a plugin

bin/compose

@@ -5,10 +5,10 @@
 const fs = require('fs')
 const vm = require('vm')
 const minimist = require('minimist')
-const composer = require('../composer')
+let composer = require('../composer')
 
 const argv = minimist(process.argv.slice(2), {
-    string: ['apihost', 'auth', 'deploy', 'lower', 'entity', 'entities'],
+    string: ['apihost', 'auth', 'deploy', 'lower', 'entity', 'entities', 'string'],
     boolean: ['insecure', 'encode', 'json', 'version', 'quiet'],
     alias: { auth: 'u', insecure: 'i', version: 'v' }
 })
@@ -40,10 +40,18 @@ if (argv._.length !== 1 || count > 1 || argv.deploy === '' || argv.entity === ''
     console.error('  -i, --insecure         bypass certificate checking')
     console.error('  -v, --version          output the composer version')
     console.error('  --quiet                omit detailed diagnostic messages')
+    console.error('  --plugin PLUGIN        register a composer plugin')
     process.exit(127)
 }
 
 try {
+    switch (typeof argv.plugin) {
+        case 'string':
+            composer = composer.register(require(argv.plugin))
+            break
+        case 'object':
+            for (let plugin of argv.plugin) composer = composer.register(require(plugin))
+    }
     const filename = argv._[0]
     let source
     try {