Update hoe to 3.16.0.

=== 3.16.0 / YYYY-MM-DD

* 1 minor enhancement:

  * Updated compiler plugin dependency for rake-compiler to 1.x.

* 2 bug fixes:

  * Fixed rdoc cmd to be more resilient to ruby version changes (w/ isolate)
  * Relaxed rake dependency to < 13 to fix against latest release.

=== 3.15.3 / 2016-11-17

* 1 bug fix:

  * Call Gem::Specification.reset after installing a gem. (segiddins)

(taca)