Remove obsolete code (php 5.6 support) (#41)

Closes #39

filter_plugins/php.py

@@ -1,16 +1,10 @@
 def php_default_upstream_socket(php_version):
-    if php_version == '5.6':
-        return '/run/php5-fpm.sock'
-    else:
     return '/run/php/php%s-fpm.sock' % php_version
 
 def php_default_upstream_name(php_version):
     return 'default_php_%s' % php_version
 
 def php_fpm_service(php_version):
-    if php_version == '5.6':
-        return 'php5-fpm'
-    else:
     return 'php%s-fpm' % php_version
 
 class FilterModule(object):