Travis is still using Java 1.6.

We can't load a 1.7 compiled JAR into HBase which is running under a
1.6 JVM. Also, we must specify source and target as Maven defaults
these values to 1.5. Additionally, since source is specified
regardless of the value (even if it matches the compiling JDK), we
must specify -bootclasspath to point to rt.jar directly otherwise we
get the following warning:

[WARNING] bootstrap class path not set in conjunction with -source 1.6

You can read about the reasons for this warning here:

https://blogs.oracle.com/darcy/entry/bootclasspath_older_source