Fix sed command error in Mac OS

Fix issue #CE-23

https://jira.hyperledger.org/browse/CE-23

Change-Id: I5d2ae66f0a6eed4e3a30ee06e5ff302cc9015d66
Signed-off-by: Haitao Yue <hightall@me.com>

Makefile

@@ -6,6 +6,12 @@ RESET  := $(shell tput -Txterm sgr0)
 THEME?=basic
 STATIC_FOLDER?=themes\/${THEME}\/static
 TEMPLATE_FOLDER?=themes\/${THEME}\/templates
+SYSTEM=$(shell uname)
+ifeq ($(SYSTEM), Darwin)
+	SED = sed -ix
+else
+	SED = sed -i
+endif
 
 .PHONY: \
 	all \
@@ -40,8 +46,8 @@ redeploy: ##@Service Redeploy single service, Use like "make redeploy service=da
 	bash scripts/redeploy.sh ${service}
 
 initial-env: ##@Configuration Initial Configuration for dashboard
-	sed -i 's/\(STATIC_FOLDER=\).*/\1${STATIC_FOLDER}/' .env
-	sed -i 's/\(TEMPLATE_FOLDER=\).*/\1${TEMPLATE_FOLDER}/' .env
+	$(SED) 's/\(STATIC_FOLDER=\).*/\1${STATIC_FOLDER}/' .env
+	$(SED) 's/\(TEMPLATE_FOLDER=\).*/\1${TEMPLATE_FOLDER}/' .env
 
 start: ##@Service Start service
 	@$(MAKE) initial-env