timestamp parsing

@imlucas 
logparse-spec.md
reformatted the example since there should be line breaks after each log line

patterns.js
- added timestamp patterns
Please improve naming of these (eg just say MongoDB < 2.4 in a comment).
See previous for conditional extra space. Also looks like the difference here is case 1 includes ms, but case 2 does not.  If you haven't yet, check out https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp#grouping-back-references