Compiling version of the postgres_exporter.

This is based on the mysqld_exporter, but drastically changes how metrics are
discovered and enumerated since postgres already very closely follows the
Prometheus format.

.gitignore

@@ -0,0 +1,7 @@
+.build
+mysqld_exporter
+*.tar.gz
+*.test
+*-stamp
+.idea
+*.iml