Remove use of assert module (#721)

Author: achingbrain

lib/levelup.js

@@ -7,7 +7,6 @@ const IteratorStream = require('level-iterator-stream')
 const Batch = require('./batch')
 const errors = require('level-errors')
 const supports = require('level-supports')
-const assert = require('assert')
 const catering = require('catering')
 const getCallback = require('./common').getCallback
 const getOptions = require('./common').getOptions
@@ -54,7 +53,9 @@ function LevelUP (db, options, callback) {
     throw error
   }
 
-  assert.strictEqual(typeof db.status, 'string', '.status required, old abstract-leveldown')
+  if (typeof db.status !== 'string') {
+    throw new Error('.status required, old abstract-leveldown')
+  }
 
   this.options = getOptions(options)
   this._db = db