Format message put into slack

[Vineeth-Mohan]

As of now , the message put into slack is as raw text and link.
Rather , it would be good to have the message like below

[schemar]

And as @nornagon wrote:

The messages phabulous sends are difficult to visually parse. Instead of:

person closed D4281: Add things to the thing by committing rTd74ade4cded6: Add things to the thing. ([More info]()) otherperson updated the test plan for D4311: Fix some things. ([More info]())

Adding some variation in formatting makes it easier to focus on the different parts of the message (what was done, who did it, what did they do it to):

**person** closed **D4281: Add things to the thing** by committing **rTd74ade4cded6: Add things to the thing**. ([More info]()) **otherperson** updated the test plan for **D4311: Fix some things**. ([More info]())