#15 Can't run JAR with java version lower than 8

When someone tries to run the JAR file for the 0.0.8 release, the following error message is shown:

rui@debian:~/Downloads$ java -jar Space-Faring-0.0.8.jar
Exception in thread "main" java.lang.UnsupportedClassVersionError: spacefaring/Spacefaring : Unsupported major.minor version 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)

I'm far from a Java expert, but from a quick search I gathered that this sort of error is thrown when JDK8 is used to compile code that is executed by an older java interpreter.

So, two things:
- is it possible to implement a Java version check that is able to provide a better error message?
- could you provide a JAR file that was built with Java7 or even Java6?

[Astrometric]

Java7 is no longer supported by Oracle. If there is a compelling reason to make it backwards compatible, then that might be considered.