Throws ugly warning if installed.json does not exist

Running concise may print this:

```
PHP Warning:  file_get_contents(/home/travis/build/kounta/kounta/vendor/elliotchance/concise/src/Concise/../../vendor/composer/installed.json): failed to open stream: No such file or directory in /home/travis/build/kounta/kounta/vendor/elliotchance/concise/src/Concise/Version.php on line 9
PHP Stack trace:
PHP   1. {main}() /home/travis/build/kounta/kounta/vendor/elliotchance/concise/bin/concise:0
PHP   2. Concise\Version->getConciseVersion() /home/travis/build/kounta/kounta/vendor/elliotchance/concise/bin/concise:7
PHP   3. Concise\Version->getVersionForPackage() /home/travis/build/kounta/kounta/vendor/elliotchance/concise/src/Concise/Version.php:21
PHP   4. file_get_contents() /home/travis/build/kounta/kounta/vendor/elliotchance/concise/src/Concise/Version.php:9
```