Remove PHP 5.4 and 5.5 from text matrix

Author: Eugene Leonovich

.travis.yml

@@ -6,8 +6,6 @@ services:
   - docker
 
 env:
-  - IMAGE='php:5.4-cli' TNT_CLIENT=pecl
-  - IMAGE='php:5.5-cli' TNT_CLIENT=pecl
   - IMAGE='php:5.6-cli' TNT_CLIENT=pecl
   - IMAGE='php:7.0-cli' TNT_CLIENT=pecl
   - IMAGE='php:7.1-cli' TNT_CLIENT=pecl