Issue #3: DEBUG level error

- added missing if case for debug
- fixes #3

Author: hameno

src/main/java/de/psdev/slf4j/android/logger/AndroidLoggerAdapter.java

@@ -417,7 +417,7 @@ public void info(final String msg, final Throwable t) {
      * Is this logger instance enabled for the WARN level?
      *
      * @return True if this Logger is enabled for the WARN level, false
-     *         otherwise.
+     * otherwise.
      */
     @Override
     public boolean isWarnEnabled() {
@@ -719,6 +719,9 @@ private static LogLevel stringToLevel(final String levelStr) {
         if ("verbose".equalsIgnoreCase(levelStr)) {
             return LogLevel.TRACE;
         }
+        if ("debug".equalsIgnoreCase(levelStr)) {
+            return LogLevel.DEBUG;
+        }
         if ("info".equalsIgnoreCase(levelStr)) {
             return LogLevel.INFO;
         }