Speed up CircleCI builds

To achieve faster feedback cycles for our feature PRs this change
reduces the average buildtime from 35 to ~6min by utilising their new
2.0 offering based on docker and nomad. We make use of parallel build
steps wherever possible so that the duration is determined by the
slowest test suite (p2p).

This is an intermediate step until we move our CI/CD completely
on-premise for more control and added security.

scripts/dep_utils/checkout.sh

@@ -1,5 +1,7 @@
 #! /bin/bash
 
+set -ex
+
 set +u
 if [[ "$DEP" == "" ]]; then
 	DEP=$GOPATH/src/github.com/tendermint/tendermint/Gopkg.lock