Revert d8a57f7; introduces spurious newlines when encoding TextMarshaler

Commit d8a57f7 in encode.go:

  fixing an encoding error where subelements of a table appear on the
  same line

wasn't actually a proper fix, and introduces spurious newlines instead.

I believe the motivation of this commit was observing datetime objects
come out like:

  Int = 1Date = 2014-05-11T12:30:40Z

but that was due to time.Time objects not being treated like primitives, and
being treated like a struct instead (time.Time's Kind is reflect.Struct).

This commit includes tests in TextEncode that show the error in d8a57f7.