CTA to set up membership

[stackptr]

Added link to collective page that sends user to edit profile or edit membership pages.

Resolves #71

Notes:

• leveldown package consistently fails the node-gyp rebuild command during install, had to rev to later version to setup repo locally. Seems to be a known issue for older versions of the package
• Still digging around to clarify when a user has an active membership to a collective, since in that case it's not as imperative to message this information (and at the very least, could resolve language from "Setup or edit" to one or the other)
• Administrate collective link seems to always show up, both locally and on sudo-humans

[rcsheets]

Looks good to me. Thanks for the contribution!!