use go mod

[stackdump]

updated to allow go mod usage from factomd project

[stackdump]

Will still need to resolve some warnings after swapping to go-mod

go mod tidy
factom/wallet/wsapi imports
        github.com/FactomProject/factom/wallet: module github.com/FactomProject/factom@latest found (v0.3.5), but does not contain package github.com/FactomProj
ect/factom/wallet
factom tested by
        factom.test imports
        github.com/FactomProject/factom/wallet/wsapi: module github.com/FactomProject/factom@latest found (v0.3.5), but does not contain package github.com/FactomProject/factom/wallet/wsapi
factom/wallet/wsapi imports
        github.com/FactomProject/btcutil/certs tested by
        github.com/FactomProject/btcutil/certs.test imports
        github.com/FactomProject/btcutil imports
        github.com/FactomProject/btcd/btcec: module github.com/FactomProject/btcd@latest found (v0.3.5), but does not contain package github.com/FactomProject/b
tcd/btcec

At least one of these is resolved by another PR - but will likely require another pass to make this clean.

[PaulBernier]

This was superseded by #144, resolving