print exceptions to stderr instead of silently dropping them

Signed-off-by: Denys Smirnov <denys@sourced.tech>

Author: Denys Smirnov

native/src/main/java/bblfsh/Main.java

@@ -12,6 +12,7 @@ public static void main(String args[]) {
         } catch (CloseException e) {
             System.exit(0);
         } catch (DriverException e) {
+            e.printStackTrace(System.err);
             System.exit(1);
         }
     }