Run merl tests together with erlydtl tests.

Avoid always running the merl tests when only compiling.

cf. richcarl/merl#6

rebar.config

@@ -14,9 +14,11 @@
  ]}.
 
 {pre_hooks,
- [{compile, "make -C $REBAR_DEPS_DIR/merl all"},
-  {"freebsd", compile, "gmake -C $REBAR_DEPS_DIR/merl all"},
+ [{compile, "make -C $REBAR_DEPS_DIR/merl all -W test"},
+  {"freebsd", compile, "gmake -C $REBAR_DEPS_DIR/merl all -W test"},
   {eunit,
    "erlc -I include/erlydtl_preparser.hrl -o test"
-   " test/erlydtl_extension_testparser.yrl"}
+   " test/erlydtl_extension_testparser.yrl"},
+  {eunit, "make -C $REBAR_DEPS_DIR/merl test"},
+  {"freebsd", eunit, "make -C $REBAR_DEPS_DIR/merl test"}
  ]}.