1.1.14 breaks compatibility with Java 7

[supersam654]

Upgrading from 1.1.13 to 1.1.14 broke our asset pipeline because we were running Java 7 (which is the version in default-jre in Ubuntu 14.04). Our stacktrace starts with:

Closure::Error: Exception in thread "main" java.lang.UnsupportedClassVersionError: com/google/javascript/jscomp/CommandLineRunner : Unsupported major.minor version 52.0

After doing a bit of digging it looks like the compiler is now getting built with a newer version of Java: https://stackoverflow.com/questions/10382929/how-to-fix-java-lang-unsupportedclassversionerror-unsupported-major-minor-versi

I believe the actual closure-compiler project switched to Java 8 towards the end of 2017: google/closure-compiler#2672.

Assuming this isn't just a silly mistake I'm making, I propose that 1.1.14 should be yanked (perhaps release 1.1.15 that just reverts back to 1.1.13 functionality) and a 2.0.0 should be released with the contents of 1.1.14.