fix incompatible go version in older Ubuntu (ex. 16.04)

[Detoo]

hi, I noticed that this particular line:

sudo go build -o $GOPATH/bin/pocket ./app/cmd/pocket_core/main.go

would fail on older Ubuntu (ex. 16.04) because the system go version is too old 1.10

was able to fix it by simply removing the sudo so it uses the newer go version installed per README