RFC-3164 dates have leading zero before date when date has only one digit

Hi,

when using glossy to produce RFC-3164 messages and the day of month only has one digit, the resulting timestamp did not have a leading space before the date (as defined in the RFC). This was due to the replace whitespace statement.

I fixed this issue by filtering and trimming the message parts prior to joining them. I also added a test case to test/produce.js.

Best,
Alex