Flux 1.6.0

This release improves existing features, and has some new goodies like
regexp tag filtering and multiple sync paths. Have fun!

We also have a new contributing guide.

Fixes

• Update example manifests to Kubernetes 1.9+ API versions
  weaveworks/flux#1322
• Operate with more restricted RBAC permissions
  weaveworks/flux#1298
• Verify baked-in host keys (against known good fingerprints) during
  build
  weaveworks/flux#1283
• Support authentication for GKE, AWS, etc., when fluxctl does
  automatic port forwarding
  weaveworks/flux#1284
• Respect tag filters in fluxctl release ..., unless --force is
  given
  weaveworks/flux#1270

Improvements

• Cope with ':' characters in resource names
  weaveworks/flux#1282
• Accept multiple --git-path arguments; sync (and update) files in
  all the paths given
  weaveworks/flux#1297
• Use image pull secrets attached to service accounts, as well as
  those attached to workloads themselves
  weaveworks/flux#1291
• You can now filter images using regular expressions (in addition to
  semantic version ranges, and glob patterns)
  weaveworks/flux#1292

Thanks

Thank you to the following for contributions: @Alien2150,
@ariefrahmansyah, @brandon-bethke-neudesic, @bzon, @dholbach,
@dkerwin, @hartmut-pq, @hiddeco, @justinbarrick, @petervandenabeele,
@nicolerenee, @rndstr, @squaremo, @stefanprodan, @stephenmoloney.