* Update to using go mod from dep

* Remove references to make get_vendor_deps

* Specify go version

* Set GO111MODULE=on and add -mod=readonly

* Fix exported env

* switch to using go1.12 everywhere

* Fix test scripts

* Typo:

* Prepend GO111MODULE=on

* remove dep cache

* Revert "remove dep cache"

This reverts commit 45117bda

Signed-off-by: Ismail Khoffi <Ismail.Khoffi@gmail.com>

* bring back the dependency cache and change it to cache modules instead
of vendored deps; also:

 - bump version for dependency cache
 - bump version on pkg-cache (includes modules directory)

Signed-off-by: Ismail Khoffi <Ismail.Khoffi@gmail.com>

* remove some more traces of dep:
 - remove Gopkg.(toml | lock)
 - update contributing guidlines
 - set global default in circleci (GO111MODULE=on)

Signed-off-by: Ismail Khoffi <Ismail.Khoffi@gmail.com>

* global var failed for `test_cover` with
`go: unknown environment setting GO111MODULE=true`
although the var was `GO111MODULE: on`

Signed-off-by: Ismail Khoffi <Ismail.Khoffi@gmail.com>

* Changelog pending entry

Signed-off-by: Ismail Khoffi <Ismail.Khoffi@gmail.com>

* Add bbolt dependency to go.mod

Signed-off-by: Ismail Khoffi <Ismail.Khoffi@gmail.com>

* move -mod=readonly to build flags