update sdk version to 2.4.0

Author: FirenzesEagle

pom.xml

@@ -18,7 +18,7 @@
  <plugin.maven-compiler>3.1</plugin.maven-compiler>
 
  <!-- lib versions -->
- <weixin-java-mp.version>2.3.1</weixin-java-mp.version>
+ <weixin-java-mp.version>2.4.0</weixin-java-mp.version>
  <junit.version>4.12</junit.version>
  <slf4j.version>1.7.21</slf4j.version>
  <spring.version>4.2.6.RELEASE</spring.version>
@@ -37,7 +37,7 @@
  <plugin.pmd.version>3.5</plugin.pmd.version>
  <plugin.findbugs.version>3.0.1</plugin.findbugs.version>
  </properties>
- 
+
  <build>
  <finalName>wechatService</finalName>
  <plugins>