replacement of es5 functons to es6 classes feat p5.filter (#526)

* replacement of es5 functons to es6 classes feat p5.filter

* set Filter class as default and rest as named export

Author: endurance21

src/app.js

@@ -33,7 +33,11 @@ p5.AudioIn = AudioIn;
 import Effect from './effect';
 p5.Effect = Effect;
 
-import './filter';
+import Filter, { LowPass, HighPass, BandPass } from './filter';
+p5.Filter = Filter;
+p5.LowPass = LowPass;
+p5.HighPass = HighPass;
+p5.BandPass = BandPass;
 
 import EQ from './eq';
 p5.EQ = EQ;
@@ -67,6 +71,7 @@ p5.Compressor = Compressor;
 
 import './soundRecorder';
 
+
 import peakDetect from './peakDetect';
 p5.peakDetect = peakDetect;