Minor - remove StringUtils#getStackTrace

- Remove StringUtils#getStackTrace in favor of Guava's Throwables#getStackTraceAsString

src/main/java/fr/xephi/authme/util/StringUtils.java

@@ -4,8 +4,6 @@ import net.ricecode.similarity.LevenshteinDistanceStrategy;
 import net.ricecode.similarity.StringSimilarityService;
 import net.ricecode.similarity.StringSimilarityServiceImpl;
 
-import java.io.PrintWriter;
-import java.io.StringWriter;
 import java.util.Arrays;
 
 /**
@@ -108,25 +106,6 @@ public final class StringUtils {
         return join(delimiter, Arrays.asList(elements));
     }
 
-    /**
-     * Get a full stack trace of an exception as a string.
-     *
-     * @param exception The exception.
-     *
-     * @return Stack trace as a string.
-     */
-    public static String getStackTrace(Exception exception) {
-        // Create a string and print writer to print the stack trace into
-        StringWriter stringWriter = new StringWriter();
-        PrintWriter printWriter = new PrintWriter(stringWriter);
-
-        // Print the stack trace into the print writer
-        exception.printStackTrace(printWriter);
-
-        // Return the result as a string
-        return stringWriter.toString();
-    }
-
     /**
      * Format the information from a Throwable as string, retaining the type and its message.
      *