IP_STATUS_FILE and routing improvements (#130)

- Obtains VPN public IP address from routing table
- Logs and writes VPN Public IP address to `/ip` as soon as VPN is up
- Obtain port forward, logs it and writes it as soon as VPN is up
- Routing fully refactored and tested
- Routing reads from `/proc/net/route`
- Routing mutates the routes using `ip route ...`

go.mod

@@ -3,6 +3,7 @@ module github.com/qdm12/private-internet-access-docker
 go 1.13
 
 require (
+	github.com/golang/mock v1.4.3
 	github.com/kyokomi/emoji v2.1.0+incompatible
 	github.com/qdm12/golibs v0.0.0-20200329231626-f55b47cd4e96
 	github.com/stretchr/testify v1.5.1