Fix conf path in systemd unit file

Add missing instruction in README

README.md

@@ -11,6 +11,7 @@ Application to display Helios4 system status for i2c OLED screen.
 
 ```
 git clone https://github.com/helios-4/sys-oled.git
+cd sys-oled
 sudo ./install.sh
 ```
 

system/sys-oled.service

@@ -2,7 +2,7 @@
 Description=System Starting on OLED Display
 
 [Service]
-EnvironmentFile=/etc/sys-oled.conf
+EnvironmentFile=/usr/local/etc/sys-oled.conf
 ExecStart=/usr/bin/python /usr/local/bin/sys-oled --display ${DISPLAY}
 
 [Install]