example: Add a repeating timer sample

Tested:
    Ran through unit test suite and manually executed the example
    program to make sure it works as expected.

Change-Id: I77cffdd038df4eab774f0d162f49273650638ad6
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/example/Makefile.am b/example/Makefile.am
index 7d4be73..96f2faa 100644
--- a/example/Makefile.am
+++ b/example/Makefile.am
@@ -10,4 +10,8 @@
 heartbeat_SOURCES = heartbeat.cpp
 heartbeat_LDADD = $(SDEVENTPLUS_LIBS)
 
+noinst_PROGRAMS += heartbeat_timer
+heartbeat_timer_SOURCES = heartbeat_timer.cpp
+heartbeat_timer_LDADD = $(SDEVENTPLUS_LIBS)
+
 endif