Fix maven build errors.

[zgypa]

This pull request addresses the following error at mvn install.

[ERROR] COMPILATION ERROR :
[INFO] -------------------------------------------------------------
[ERROR] Source option 7 is no longer supported. Use 8 or later.
[ERROR] Target option 7 is no longer supported. Use 8 or later.
[INFO] 2 errors
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE

Also, ignoring the target/ folder.