Reduce code block widths when possible

The goal here is to make code blocks concise so they only expand past the content when necessary.

To achieve this, I deleted a bunch of whitespace from the beginning/end of code blocks and also modified some of the REST API curl commands to use the `--user` flag rather than specify the username and access key in the URL.

The REST API still needs work though. I haven't updated all curl examples because some endpoints have sections which need to be replaced by the user like this one:
```bash
curl https://saucelabs.com/rest/v1/sauceUsername/jobs/YOUR_JOB_ID \
  --user sauceUsername:sauceAccessKey
```
If we give the user the code like this it is difficult to modify the YOUR_JOB_ID because the cursor is on the `--user` line and it is difficult to swap YOUR_JOB_ID with an actually JOB_ID.

@OniOni suggested we might have it be displayed as multiple lines but copy to a single line.
We could also try to put the dynamic part of the curl code at the end so that users can edit the final line and replace the variable.

Any thoughts @sah?