Include rather than duplicate content in the docs

[lukemarsden]

there will be duplication of content in places, e.g. "how to install dotmesh" will appear in the tutorial

It would be nice if we could have these in include files from the get go, so that multiple copies don't end up getting stale and out of date

is gohugoio/hugo#247 (comment) the right way to do this?

[lukemarsden]

this is a good example of a chunk that would be nice to deduplicate, from the library tutorial

### Make sure you have the hub as a remote

Check the output of the following command to see if `hub` is listed as a remote.

{{< copyable name="step-04b" >}}
dm remote -v
{{< /copyable >}}

If it isn't, add it.
Set an environment variable with your Dothub username in it:

```plain
export HUB_USERNAME=<username>
\```
{{< copyable name="step-09" >}}
dm remote add hub ${HUB_USERNAME}@dothub.com
{{< /copyable >}}

You will be prompted for your API key, which you can get from the [Settings/API Key page](https://dothub.com/ui/settings/apikey).

[Godley]

Presume this is no longer relevant, reopen if it's a problem