This function lets the user send Emails with Attachments using Sendgrid
mailSend(body, subject, attachment = NULL, to = credentials$to,
from = credentials$from, creds = NA, quite = FALSE)
Character. Body for the email
Character. Subject for the email
Vector. All objects which will be sent as attachment
Character. Email of the person who will recevie the email
Character. Email of the person who send the email
Character. Credential's user (see get_credentials)
Boolean. Keep quite or display messages?