Per kmixter's suggestion, install metrics headers under /usr/include/metrics.

Also, move file installation to the metrics ebuild.

Review URL: http://codereview.chromium.org/2087002
diff --git a/metrics/Makefile b/metrics/Makefile
index 16e1d9f..5ce0caf 100644
--- a/metrics/Makefile
+++ b/metrics/Makefile
@@ -63,14 +63,5 @@
 	network_states.h \
 	power_states.h
 
-install:
-	install $(CLIENT) $(DESTDIR)/usr/bin
-	install $(DAEMON) $(DESTDIR)/usr/bin
-	install $(LIB) $(DESTDIR)/usr/lib
-	install $(SHAREDLIB) $(DESTDIR)/usr/lib
-	install metrics_library.h $(DESTDIR)/usr/include
-	install syslog_parser.sh $(DESTDIR)/usr/bin
-	install omaha_tracker.sh $(DESTDIR)/usr/sbin
-
 clean:
 	rm -f $(CLIENT) $(DAEMON) $(LIB) $(SHAREDLIB) $(TESTDAEMON) *.o
diff --git a/metrics/README b/metrics/README
index 6d011db..2c7072d 100644
--- a/metrics/README
+++ b/metrics/README
@@ -28,7 +28,7 @@
   preferred.
 
 - To access the metrics library API in the module, include the
-  <metrics_library.h> header file. The file is installed in
+  <metrics/metrics_library.h> header file. The file is installed in
   $SYSROOT/usr/include/ when the metrics library is built and
   installed.