How does TubeMQ support the use of the Java 7 environment?

[gosonzhang]

Considering that the business environment using TubeMQ is java 7 and does not allow upgrades, it's a better support method to adjust the je version to a lower version than 7.3.7, such as 6.1.5.

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考虑到使用TubeMQ的商业环境是Java 7，并且不允许升级情况，如果业务需要使用TubeMQ,将je版本调整为低于7.3.7（例如6.1.5）的版本是一种比较好的支持方法。

[gosonzhang]

see #72

[gosonzhang]

@tisonkun I found that in the jdk 1.7 environment, compiling the entire project will report the following error, can help to see how to deal with it?

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我发现在jdk 1.7环境，编译整个工程会报如下这个错误，能帮忙看看怎么处理吗？

[INFO] --- maven-checkstyle-plugin:3.1.0:check (checkstyle) @ tubemq ---
[WARNING] Error injecting: org.apache.maven.plugins.checkstyle.CheckstyleViolationCheckMojo
java.lang.TypeNotPresentException: Type org.apache.maven.plugins.checkstyle.CheckstyleViolationCheckMojo not present
        at org.eclipse.sisu.space.URLClassSpace.loadClass(URLClassSpace.java:147)
        at org.eclipse.sisu.space.NamedClass.load(NamedClass.java:46)
        at org.eclipse.sisu.space.AbstractDeferredClass.get(AbstractDeferredClass.java:48)
        at com.google.inject.internal.ProviderInternalFactory.provision(ProviderInternalFactory.java:81)
        at com.google.inject.internal.InternalFactoryToInitializableAdapter.provision(InternalFactoryToInitializableAdap