Add local time zone & time formatting configuration

[friedbunny]

Use moment.js to add option to display timestamps in local time, but default to UTC. Also add the option to customize the time formatting, using moment.js conventions.

Adds moment.js dependency.

Adds options:

config.UTC: TRUE
config.timeFormat: moment.defaultFormat

[coveralls]

Coverage decreased (-27.56%) when pulling d4784b7 on friedbunny:local-timezone into 3be44f0 on mrrama:master.

[friedbunny]

Just a note: rudely, my PR does break the tests and changes the default time format to YYYY-MM-DDTHH:mm:ssZ, i.e., 2014-11-10T23:55:42-00:00. Moment.js converts Z to 00:00 for UTC, while bunyan leaves it as simply Z, i.e., 2014-11-10T23:55:42:20Z.

Old format would be 'YYYY-MM-DDTHH:mm:ss:SS[Z], but this doesn't convert Z to the proper zone. I'm lazy and didn't bother to hack around this, sorry.

This seems like a moment.js bug, actually... I couldn't get moment.toISOString() to actually do what their docs said it would.

[coveralls]

Coverage decreased (-27.56%) when pulling 1ca794b on friedbunny:local-timezone into 3be44f0 on mrrama:master.