Add ability to customize email subjects

[playpauseandstop]

Right now each email, which send by Flask-Security, has static subject, but in most cases we need to customize email subject due to different applicaiton.

Yeah, it also possible to do in current implementation as:

from flask import Flask
from flask.ext.mail import Mail
from flask.ext.security import Security

app = Flask('appname')
mail = Mail(app)
...
def send_mail(message):
    if message.subject == 'Welcome':
        message.subject = 'Confirm your account'
    mail.send(message)
...
security = Security(app, datastore)
app.extensions['security']._send_mail_task = send_mail

But I think it's ugly ability and more natural way is to adding default subjects similar to default messages and customize they as SUBJECT_WELCOME in project settings.

What do you think?

[mattupstate]

Thanks for pointing this out. Just something I totally overlooked. I"ll add this feature as soon as I can.

[playpauseandstop]

Thanks for your response! Will wait for news here :)

[mattupstate]

Starting work on this in #47

[playpauseandstop]

Great! Will update to dev version in my project to use this ability!

[mattupstate]

@playpauseandstop I've released an update with this feature.