Document tzdata dependency

[jseldess]

Fixes #4433.

[cockroach-teamcity]

This change is 

[jseldess]

@bdarnell, is this sufficient, or do we need to explicitly call this out in the install pages and/or the deployment tutorials?

[cockroach-teamcity]

http://cockroach-docs-review.s3-website-us-east-1.amazonaws.com/fa25f745fec15c78e0d2d49d7cb4676ad482e36d/

[cockroach-teamcity]

http://cockroach-docs-review.s3-website-us-east-1.amazonaws.com/698596db8b972095e6cb7d315e08be9115481010/

[bdarnell]

Since the tzdata package is usually installed by default (and is nearly always present on development machines), it's probably fine to only mention it here. But technically it's an install-time requirement at the same level as glibc and libncurses.

[bdarnell]

"machines", not VMs - we don't know or care whether they're virtualized.

This does not apply to docker-based deployments. The tzdata package is included in the docker image and is update with each patch release of cockroachdb.

[jseldess]

Done. I'll work on one more commit adding the tzdata error to the common errors page.

[cockroach-teamcity]

http://cockroach-docs-review.s3-website-us-east-1.amazonaws.com/ecdd2b6c3bcf106119fae8b259cf0fb3144406ef/

[cockroach-teamcity]

http://cockroach-docs-review.s3-website-us-east-1.amazonaws.com/b8ff369935398bba164951eefa93a692bf168c40/

[jseldess]

@bdarnell, PTAL again.

I'm not sure why the build is failing. The anchors it's complaining about are perfectly fine.

[cockroach-teamcity]

http://cockroach-docs-review.s3-website-us-east-1.amazonaws.com/b8ff369935398bba164951eefa93a692bf168c40/

[cockroach-teamcity]

http://cockroach-docs-review.s3-website-us-east-1.amazonaws.com/e683b9b4fe9c50db2eeaf41b457698dfc234ff66/

[cockroach-teamcity]

http://cockroach-docs-review.s3-website-us-east-1.amazonaws.com/5a37e6993a3677249230298f294730d6daed8819/