docs: update readme examples (#6)

Update examples in readme

README.md

@@ -10,8 +10,8 @@ A pair of {source, sink} streams that are internally connected,
 This can be used to construct pipelines that are connected.
 
 ``` js
-var pipe = require('it-pipe')
-var pair = require('it-pair')
+import { pipe } from 'it-pipe'
+import { pair } from 'it-pair'
 
 var p = pair()
 
@@ -35,9 +35,9 @@ around servers. Use `it-pair/duplex` to get two duplex streams
 that are attached to each other.
 
 ``` js
-var DuplexPair = require('it-pair/duplex')
+import { duplex } from 'it-pair/duplex'
 
-var d = DuplexPair()
+var d = duplex()
 
 //the "client": pipe to the first duplex and get the response.
 pipe(