Use go mod download to install deps on travis-ci. Add cache for travis-ci.

Signed-off-by: Artemiy Ryabinkov <getlag@ya.ru>

travis/install.bash

@@ -1,14 +0,0 @@
-#!/usr/bin/env bash
-set -eux
-
-go get -u github.com/cockroachdb/apd
-go get -u github.com/shopspring/decimal
-go get -u gopkg.in/inconshreveable/log15.v2
-go get -u github.com/jackc/fake
-go get -u github.com/lib/pq
-go get -u github.com/hashicorp/go-version
-go get -u github.com/satori/go.uuid
-go get -u github.com/sirupsen/logrus
-go get -u github.com/pkg/errors
-go get -u go.uber.org/zap
-go get -u github.com/rs/zerolog