Updates requirements
Updates requirements

- PHP: `^5.5 || ^7.0`
- require-dev:
  - zend-http => `^2.5.4`
  - zend-server => `^2.6.1`
  - zend-stdlib => `^2.7 || ^3.0`
  - zendxml => `^1.0.2`

These changes will allow updating dependencies and dependent components with forwards-compatibility features.

MadCat34/zend-json,zendframework/zend-json