Improvement: Improve bugInstance message, and support Japanese

Change set

• Improve message of each bug patterns, and create unit tests to check messages (issue #39)
• Translate bug pattern message to Japanese (issue #41)

How to use with Maven

      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>findbugs-maven-plugin</artifactId>
        <version>3.0.1</version>
        <configuration>
          <plugins>
            <plugin>
              <groupId>jp.skypencil.findbugs.slf4j</groupId>
              <artifactId>bug-pattern</artifactId>
              <version>1.2.4</version>
            </plugin>
          </plugins>
        </configuration>
      </plugin>