Adds a second attempt to send the HTTP request in case of a network fail...

We found few examples for HTTP failures causing SMS's sending failure.
This is a simple approach to reduce the chance for failure.
Last comment I have, I promise!

Maybe it's better to have a 'tries' counter going backwards from 3 to 1, instead of a meaningless 'index' counter going from 1 to 3. Think about it, there's nothing 'index'-ish about this.

This way:

````
tries = 3
# ...
if tries > 0
# ...
````