Add StyleCI badge

Author: DivineOmega

README.md

@@ -2,6 +2,7 @@
 
 [![Build Status](https://travis-ci.org/DivineOmega/php-hcl-parser.svg?branch=master)](https://travis-ci.org/DivineOmega/php-hcl-parser)
 [![Coverage Status](https://coveralls.io/repos/github/DivineOmega/php-hcl-parser/badge.svg?branch=master)](https://coveralls.io/github/DivineOmega/php-hcl-parser?branch=master)
+[![StyleCI](https://styleci.io/repos/128951643/shield?branch=master)](https://styleci.io/repos/128951643)
 
 HCL is a configuration language make by HashiCorp. HCL files are used by several HashiCorp products,
 including Terraform.