Better logs

[rynorris]

Adds timestamps, file names, line numbers and function names to log output. Fixes issues #14 (mostly) and #15.

[StefanKopieczek]

Looks good, but:

• Can we have 4 digits for line numbers just to be sure?
• If we fail to get the stack, we don't have any way to debug the problem. I almost want to say we should write an error to the log and dump stack (maybe only once per app run?) but I think it's overkill because that will absolutely never happen. [this may come back to bite me]

Also, I'm not sure if Gossip Jenkins is still up. I need to go take a look so we can be sure this will be merged to master correctly. Once you've made the 4-digit change I'll merge and then go figure out if G-J needs a kick.

[rynorris]

I think failing to get the stack is unlikely enough (basically implies an error on the fault of the runtime) that we don't need to worry about it.

Line numbers changed to 4 digits.