Add client to error event emitter (#65)

When the pool emits an error pass the client as the 2nd parameter to the `on('error')` handler.

index.js

@@ -90,7 +90,7 @@ Pool.prototype._create = function (cb) {
     this.log('connected client error:', e)
     this.pool.destroy(client)
     e.client = client
-    this.emit('error', e)
+    this.emit('error', e, client)
   }.bind(this))
 
   client.connect(function (err) {

test/events.js

@@ -60,6 +60,22 @@ describe('events', function () {
       pool.end(done)
     }, 40)
   })
+
+  it('emits error and client if an idle client in the pool hits an error', function (done) {
+    var pool = new Pool()
+    pool.connect(function (err, client) {
+      expect(err).to.equal(null)
+      client.release()
+      setImmediate(function () {
+        client.emit('error', new Error('problem'))
+      })
+      pool.once('error', function (err, errClient) {
+        expect(err.message).to.equal('problem')
+        expect(errClient).to.equal(client)
+        done()
+      })
+    })
+  })
 })
 
 function mockClient (methods) {