Lint-ing all of Weave Net is currently not desirable because:
* it would create conflicts on many branches,
* it would pollute the git history,
* etc.
and because `lint` currently lints all files except `./vendor`, this breaks Weave Net's build.
As a result, Weave Net is not using the latest commit in `build-tools`'s `master` branch, which is also source of problems:
* it limits standardisation of projects across Weaveworks,
* it limits the ability to use the latest features of `build-tools`,
* it complexifies merging changes in `build-tools` (e.g. #53 and weaveworks/weave#2694 for weaveworks/weave#2647),
* etc.
This change:
* brings Weave Net to the latest version of `build-tools` (which now supports `.lintignore` files),
* adds such a `.lintignore` file to skip all bash scripts (in order to avoid breaking the build).
`GLOB`s in `.lintignore` can then, over time and as scripts are `shfmt`-ed, be relaxed and maybe even removed.
Marc CARRE