Set compile target to JDK 1.6

I love Strucjure... it's the best of Scala pattern matching (extractors, etc.) with the best of a parser... so amazing.

We are using Strucjure in a JVM 1.6 environment (much of the corporate world is very behind where they should be) but the compiled classes have JDK 1.7 markers. I updated the project.clj file to set the compilation target to JDK 1.6.

I'd appreciate it if you could accept the patch and publish the JARs on Clojars with the 1.6 generated classes.

Thanks!