feat(helm): add service account flag to helm init

Add support for zsh to helm completion

helps with half of #2224

chore(ci): bump go 1.8.1

Fail template execution if included template fails

Updated the 'helm completion' command to take in the shell
as a parameter. Currently acceptable options are 'bash' and
'zsh'. Also fixed the completions to work with zsh in a manner
similar to what kubectl does.

Also updated the docs to reflect this change.

Closes #2201

fix(helm): fix style errors in pkg/environment

docs(chart_hooks): clarify hook execution order

fix(helm): return error when dependencies are missing

chore(*): cleanup unused travis and scripts

feat(*): update to latest gRPC and Protobuf

Add Git and Mercurial to build prerequisites

This just adds a few comments where the style linter was complaining.

Closes: #2343

Closes #2234

This upgrades a warning to an error in cases where `requirements.yaml`
contains a requirement, but it's missing in charts/

This impacts install, upgrade, and package.

Closes #2209

fix(tiller): update tls client auth policy

Effectively, this switches us to gRPC's internal version 4. This is
compatible with protoc 3.2 and grpc-go 1.2.1.

Update Slack channels

Improve get script

Added reference to plugins

ref(helm): use new debug method to standardize debug output

RequireAndVerifyClientCert => VerifyClientCertIfGiven

Closes #2310

chore(*): bump kubernetes to v1.6.2

chore(README.md): update zoom meeting link

ref(*): Regenerates protobuf files with protoc 3.2.0