Better .gitignore file

For quite some time there were files that we were simply not committing
to the repo. However, it feels unorganized and inconvenient, so let's
fix that.

The directory structure should be changed at some point, but this is
already better than what we had at previously.

Author: AlexDaniel

.gitignore

@@ -1,5 +1,15 @@
-rakudo
+.precomp
+
+# TODO we should probably move these into a subdir
 builds
 logs
-config.json
-.precomp
+irc
+stats
+all-modules
+rakudo
+rakudo-moar
+MoarVM
+moarvm
+nqp
+perl6-bench
+Perl6-Text--Table--Simple