Update Bigtable samples to v2.

[tswast]

Table of Contents generated with:

doctoc --title '**Table of Contents**' bigtable

Needs to wait for next gcloud-python launch so that googleapis/google-cloud-python#1932 can go in. Tested locally on the bigtable-v2 branch of gcloud-python with a
previous version of grpcio.

[theacodes]

I think I've mentioned this elsewhere, but the READMEs in this repository mostly just link back to the docs. I don't like the idea of having duplicate instructions here.

[theacodes]

This LGTM once everything is ready. Feel free to merge.

[tswast]

These instructions aren't duplicate. The docs contain no download or set up instructions, only code explanation.

I'm waiting on googleapis/google-cloud-python#1940 before merging.

[mbrukman]

googleapis/google-cloud-python#1940 has been merged so you're all set.

[theacodes]

The docs contain no download or set up instructions, only code explanation.

Uh, are you saying that in order for a user to use these samples they need to read both the docs and this readme? That seems wrong.

[tswast]

That seems wrong.

Seemed wrong to me, too. I got some push-back from the tech writers when I tried to add this info to the docs.

Basically, Google punishes sites for having duplicate content. https://support.google.com/webmasters/answer/66359?hl=en
So this is a compromise. Docs can explain and if they want to run, they go to the README.

I just forwarded a thread to the group that has more context.

[theacodes]

Cool, let's resolve it there. The readme here can stay.