Make CreatureException inherit from runtime_error.

tests/ExceptionTests.cpp

@@ -4,12 +4,15 @@
 #include "../src/Core/Exceptions/CreatureException.hpp"
 
 TEST_CASE("When throwing exception, what() is readable", "[Utilities]") {
+    bool hasCaught = false;
     try {
         throw CreatureException("foobar");
-    } catch (const CreatureException& e) {
+    } catch (const std::exception& e) {
+        hasCaught = true;
         INFO(e.what());
         REQUIRE(strcmp(e.what(), "foobar") == 0);
     }
+    REQUIRE(hasCaught);
 }
 
 #endif