Updated the PHP Version details.

Author: ssiddhantsharma

.github/ISSUE_TEMPLATE

@@ -14,4 +14,4 @@ Any other information you want to share that is relevant to the issue being repo
 #### Technical details:
 
 * php-http-client Version: master (latest commit: [commit number])
-* PHP Version: 5.x
+* PHP Version: 5.4 to 7.2(as of 01'February 2018)