Eliminate carriage returns when encoding text

Fixes issues #9 and #13.

From [RFC 6350](http://tools.ietf.org/html/rfc6350) section 4.1 ("TEXT"):
> A formatted text line break in a text value type MUST be represented as the character sequence backslash (U+005C) followed by a Latin small letter n (U+006E) or a Latin capital letter N (U+004E), that is, "\n" or "\N".

@brendon, can you review & make sure this solves the problem you first reported?