improved code styles #158 (#172)

* use php-cs-fixer instead of phpcodesniffer
* updated scrutinizer config
* adjusted code yules to all files
* updated CONTRIBUTING guidelines

src/Timesheet/Calculator/RateCalculator.php

@@ -37,7 +37,7 @@ class RateCalculator implements CalculatorInterface
      */
     public function calculate(Timesheet $record)
     {
-        if ($record->getEnd() === null) {
+        if (null === $record->getEnd()) {
             return;
         }
 
@@ -81,6 +81,7 @@ class RateCalculator implements CalculatorInterface
     protected function calculateRate(Timesheet $record)
     {
         $hourlyRate = (float) $record->getUser()->getPreferenceValue(UserPreference::HOURLY_RATE, 0);
+
         return (float) $hourlyRate * ($record->getDuration() / 3600);
     }
 }