Update "Reviewer suggestions" in author guide to include diversity info.

[chris-huggins]

Text was updated in eJP author guide to ask authors to consider diversity when suggesting reviewers, we should update the Reviewer author guide accordingly.

From Editorial https://elifesciences.slack.com/archives/C6MJK1RD4/p1557493855031000?thread_ts=1557492885.030800&cid=C6MJK1RD4:

"We've also just updated the author guide to reflect this. In the Initial Submissions section:

From this: "Reviewer suggestions: Authors can optionally suggest potential reviewers for their work at the Initial Submission stage. Requests to exclude individuals can also be made and must be accompanied with a brief explanation. We will make every effort to follow author requests for excluded individuals.."

To this:

Reviewer suggestions: Authors can optionally suggest potential reviewers for their work at the Initial Submission stage. Please list the names of experts who are knowledgeable in your area and could give an unbiased review of your work. To support diversity, please consider suggesting potential reviewers at an early stage of their career, women, and experts from countries other than the USA and Europe. Please do not list colleagues who are close associates, collaborators, or family members. Requests to exclude individuals can also be made and must be accompanied with a brief explanation. We will make every effort to follow author requests for excluded individuals."

This relates to the section no. 7 at the bottom of https://reviewer.elifesciences.org/author-guide/initial