Adds new truncateLastWord option and method. Tests included.

Squashed commit of the following:

commit d3192022284f064bc0381601414e8e583d0ca592
Author: Dan MacTough <danmactough@gmail.com>
Date:   Thu Nov 28 15:10:34 2013 -0500

    Add tests for truncateLastWord option

commit 7871b43eedbc2ff350f881468a333e7c2229e9cc
Author: Dan MacTough <danmactough@gmail.com>
Date:   Thu Nov 28 15:39:14 2013 -0500

    Remove debugging hints

commit bf9e28421eb9a99530eec9e366a4465c30c28ec1
Author: Dan MacTough <danmactough@gmail.com>
Date:   Thu Nov 28 15:09:08 2013 -0500

    Add new truncateLastWord option with slop factor

commit 9da88227e549a38862c3feaf83ae28e14514ebd1
Author: Dan MacTough <danmactough@gmail.com>
Date:   Thu Nov 28 15:06:22 2013 -0500

    Fix check for whether ellipsis is needed