Disable APC on CLI on Travis

`apc.enable_cli` in `php.ini`.

Because it seems to make our build/composer fail (e.g. [here](https://travis-ci.org/cargomedia/CM/jobs/40216023).
Similar to https://github.com/composer/composer/issues/264?

```
PHP Fatal error:  include(): Cannot redeclare class jsonschema\constraints\collection in phar:///home/travis/.phpenv/versions/5.4.34/bin/composer/vendor/composer/ClassLoader.php on line 269
```