Test manage members

[colbymorrison]

Depends on #446 . New files in this PR is __tests__/manage_members.test.js

Tests

• Clicking the Reset Password link calls the reset password cloud function
• AddMemberModal closes correctly (Serena wrote this one)
• With valid input, AddMemberModal calls the create user Firebase function on submit (Serena wrote this one too!)
• With invalid input new user cannot be created. Invalid input tested is 1) Not all fields filled out and 2) All fields filled out but invalid email

Notes

• I made one change to ManageTeams.js. The testing framework has a tough time managing refs, so all the Toasts were breaking in the tests, even though the tests don't use or reference the Toast. Specifically, confirmationToast.current was always null. So I changed a line from confirmationToast.current.show() to confirmationToast.current && confirmationToast.current.show(). This allows the tests to pass and doesn't change the functionality. Hope that is ok. If not, we can go another route.

Updates

• Refactored Add Member Modal test to be more concise and renamed its extension from .react.test.js to .test.js
• Use global waitForComponentToPaint function instead of defining it locally

[colbymorrison]

The add member modal tests are in addmembermodal.react.test.js, the file Serena submitted. I updated it in this PR (though I think I removed the snapshot test since it was failing, so we may want to re-add it)