Flash Message Support

[rgarbin]

Added test to send msg (simple / multiple) using flash msg.

[coveralls]

Coverage increased (+1.3%) to 73.75% when pulling 4c02cc0 on flash_msg into 60d6436 on master.

[coveralls]

Coverage decreased (-31.8%) to 40.741% when pulling 466aa9d on flash_msg into 60d6436 on master.

[coveralls]

Coverage decreased (-20.6%) to 51.852% when pulling 1f05faa on flash_msg into 60d6436 on master.

[coveralls]

Coverage decreased (-12.006%) to 60.494% when pulling 5683a41 on flash_msg into 60d6436 on master.

[anderkonzen]

LGTM!

[anderkonzen]

I didn't check the drop in coverage, but it looks good to me!

[jonatasfreitasv]

@rgarbin and @anderkonzen
Hi guys!

This PR is still valid

If yes, plz solve conflicts for merge.

Thx a lot.