Change Time.to_json to include subseconds

Since CouchDB doesn't have any equivalent auto-incrementing id fields, discerning the order in which additions took place might be problematic if there is more than one record added in a single second. This could be important for, say, logging.

I propose changing the Time.to_json monkeypatch to include sub-second precision. The change is simple: modify line 11 of monkeypatches.rb to read:

%("#{u.strftime("%Y/%m/%d %H:%M:%S.#{u.usec} +0000")}")

CouchRest and all tests should continue to work fine with this minor change.