Add user memberships

[lucasmichot]

Add user memberships features:

• https://developer.github.com/v3/orgs/members/#list-your-organization-memberships
• https://developer.github.com/v3/orgs/members/#get-your-organization-membership
• https://developer.github.com/v3/orgs/members/#edit-your-organization-membership

[GrahamCampbell]

Please indent with spaces. :P

[lucasmichot]

good catch Graham

[cursedcoder]

very good @lucasmichot do you want to add docs here either?

[lucasmichot]

Yep @cursedcoder I will do so, as for orgs webhooks

[lucasmichot]

Ping @cursedcoder

[GrahamCampbell]

@lucasmichot You need to rebase this to load the correct styleci config.

[lucasmichot]

Yep saw that done @GrahamCampbell

[GrahamCampbell]

:)

[lucasmichot]

Nice https://styleci.io/commits/648bc8614e77894532343fa4d0d762e77886af3f 👍

[stof]

the name is weird, because this method only allows to mark the membership as active.