Depend on Ranch master in examples

Otherwise they are pinned to 1.2.1.
Per discussion with @essen.

examples/tcp_echo/Makefile

@@ -1,3 +1,4 @@
 PROJECT = tcp_echo
 DEPS = ranch
+dep_ranch_commit = master
 include ../../erlang.mk

examples/tcp_reverse/Makefile

@@ -1,3 +1,4 @@
 PROJECT = tcp_reverse
 DEPS = ranch
+dep_ranch_commit = master
 include ../../erlang.mk