Add configurable timeout to config file and default to 90 sec

[lachesis]

Raise the default Barge client timeout to 90 seconds and make it configurable.

I've only briefly tested this. I'm not sure if this is the right way to add stuff to the config file. We need this because our droplet list is huge and the default 10 seconds per page timeout is too aggressive for us.

[coveralls]

Coverage increased (+0.006%) to 98.015% when pulling aac599f on lachesis:lachesis-timeouts into bc58bed on petems:master.

[petems]

Closing in favour of #283