update readme

Author: noogen

README.md

@@ -1,4 +1,6 @@
 # `bayes`: A Naive-Bayes classifier for PHP
+[![Build Status](https://travis-ci.org/niiknow/bayes.svg?branch=master)](https://travis-ci.org/niiknow/bayes)
+
 `bayes` takes a document (piece of text), and tells you what category that document belongs to.
 
 This library was ported from a nodejs lib @ https://github.com/ttezel/bayes

composer.json

@@ -26,7 +26,7 @@
   }],
   "type": "library",
   "require": {
-    "php": ">=5.6"
+    "php": ">=7.0"
   },
   "require-dev": {
     "phpunit/phpunit": "~6.3.0"