Updated supported language versions

Author: thinkingserious

.travis.yml

@@ -6,14 +6,9 @@ before_script:
 - cd test/unit
 script:
 - ../../vendor/bin/phpunit . --bootstrap bootstrap.php --filter test* --coverage-clover clover.xml
-after_script:
-- cd ..
-- phpenv local 5.4
-- phpenv local --unset
 php:
-- 5.4
-- 5.5
 - 5.6
+- 7.0
 env:
   global:
   - secure: eUN0huKA436uIkISu6V3yW01/gZHC6slBvlnprMPEhzclU2szH6qhWEXWS5CcOG6EEDBReqLZdNAwu+FC69KGFO9+6oW2GQQLSsfEViqFi/Ig2N0r4EBO4jLRebgq0GOfetPwQvJH27d8BCiloPy8rXBb5pskxSNw4B4bRyXHz4=

CONTRIBUTING.md

@@ -64,7 +64,7 @@ We welcome direct contributions to the php-http-client code base. Thank you!
 
 ##### Prerequisites #####
 
-- PHP 5.2 through 5.6
+- PHP 5.6 or greater
 - [Composer](https://getcomposer.org/)
 
 ##### Initial setup: #####