The problem is that your Java installation is out of date.
The version number (52) is Java 8, so if you are getting an exception that says 52 is not understood, then you must be running those tests using a JVM that is Java 7 or earlier. Code that is compiled for that Java 8 platform will not run on a Java 7 (or earlier) JVM.
Java 7 is out of date, and well beyond the official "end-of-life" (April 2015) .... and you should upgrade.
If you insist on using an out-of-date Java platform for your development, then you are going to need to download the source code for the selenium libraries, and recompile them using a Java 7 compiler. (And, if selenium is starting to use Java 8 features, you will need to roll back to an earlier selenium release ... or backport.)