Replace discouraged command substitution syntax in deploy script

The previous backticks command substitution syntax is discouraged in favor of the modern `$()` syntax for the reasons described here:
http://mywiki.wooledge.org/BashFAQ/082

Author: per1234

deploy.sh

@@ -1,9 +1,9 @@
 #!/bin/bash -xe
-GIT_REV=`git log --pretty=format:'%h' -n 1`
-BUILD_DATE=`date +%Y-%m-%d:%H:%M:%S`
-COMPILEINFO=`echo +$GIT_REV+$BUILD_DATE | tr -d '"'`
+GIT_REV="$(git log --pretty=format:'%h' -n 1)"
+BUILD_DATE="$(date +%Y-%m-%d:%H:%M:%S)"
+COMPILEINFO="$(echo +$GIT_REV+$BUILD_DATE | tr -d '"')"
 
-VERSION=`cat main.go| grep "const AppVersion" |cut -f4 -d " " | tr -d '"'`
+VERSION="$(cat main.go| grep "const AppVersion" |cut -f4 -d " " | tr -d '"')"
 
 #Remember to set GOROOT accordingly with your installation