Add ability to select compression algo by downloading location with file extension.

- Also update README.md with more useful examples.

contrib/backer.openrc

@@ -7,6 +7,7 @@ pidfile="/run/$SVCNAME/$SVCNAME.pid"
 
 depend() {
         need net
+        use dns
 }
 
 start_pre() {
@@ -14,4 +15,4 @@ start_pre() {
         mkdir -p /run/$SVCNAME
 }
 
-# vim: set ft=sh noet ai ts=4 sw=4 sts=4:
+# vim: set ft=sh noet ai ts=4 sw=4 sts=4: