include 7.2, add example

Author: kornrunner

.travis.yml

@@ -2,6 +2,7 @@ language: php
 
 php:
   - 7.1
+  - 7.2
   - nightly
 
 install:

README.md

@@ -1,2 +1,27 @@
-# php-keccak
-Keccak
+# php-keccak [![Build Status](https://travis-ci.org/kornrunner/php-keccak.svg?branch=master)](https://travis-ci.org/kornrunner/php-keccak)  [![Coverage Status](https://coveralls.io/repos/github/kornrunner/php-keccak/badge.svg?branch=master)](https://coveralls.io/github/kornrunner/php-keccak?branch=master)
+Pure PHP implementation of Keccak (SHA-3)
+
+## Usage
+
+```php
+<?php
+
+use kornrunner\Keccak;
+
+Keccak::hash('', 224);
+// f71837502ba8e10837bdd8d365adb85591895602fc552b48b7390abd
+
+Keccak::hash('', 256);
+// c5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470
+
+Keccak::hash('', 384);
+// 2c23146a63a29acf99e73b88f8c24eaa7dc60aa771780ccc006afbfa8fe2479b2dd2b21362337441ac12b515911957ff
+
+Keccak::hash('', 512);
+// 0eab42de4c3ceb9235fc91acffe746b29c29a8c366b7c60e4e67c466f36a4304c00fa9caf9d87976ba469bcbe06713b435f091ef2769fb160cdab33d3670680e
+
+Keccak::shake('', 128, 256);
+// 7f9c2ba4e88f827d616045507605853ed73b8093f6efbc88eb1a6eacfa66ef26
+
+Keccak::shake('', 256, 512);
+// 46b9dd2b0ba88d13233b3feb743eeb243fcd52ea62b81b82b50c27646ed5762fd75dc4ddd8c0f200cb05019d67b592f6fc821c49479ab48640292eacb3b7c4be