Customizing reporters

[alpian]

Allow an implementation of Reporter to be passed into the reporters configuration to simplify the process of supplying your own reporter.

Also add clojure.test as a default reporter

[slagyr]

I'd like to release with this included but I'm experiencing a problem. See below. Also, would you please update specjl.cli/arg-spec with the new builtin reporter?

$ lein spec -f clojure-test
java.lang.NullPointerException
at clojure.core$deref_future.invoke(core.clj:2108)
at clojure.core$deref.invoke(core.clj:2129)
at speclj.report.clojure_test.ClojureTestReporter.report_runs(clojure_test.clj:75)
at speclj.reporting$report_runs_STAR_.invoke(reporting.clj:97)
at speclj.run.standard.StandardRunner.run_and_report(standard.clj:43)
at speclj.run.standard.StandardRunner.run_directories(standard.clj:30)
at speclj.cli$do_specs$fn__1240.invoke(cli.clj:85)

[alpian]

Great! Thanks for accepting the pull-request! I will update arg-spec. I did see that NPE, but only intermittently and figured it had gone away - i will take another look asap :).