Log Message:
Update ruby-gsl to 1.16.0.4.

* Switch to rb-gsl gem.

Fri Dec 19 2014
  * Ruby/GSL 1.16.0.4
    * Optimize and extract multiplication and division operations on Fixnum
      and Float. Pull request #8 by Veselin Vasilev.
    * Fixed division in GSL::Oper for GSL::Vector::Col. Issue #9.

Tue Oct 21 2014
  * Ruby/GSL 1.16.0.3
    * Fixed RDoc issues. Issue #6 by @bigtunacan.
    * Fixed $LOAD_PATH problem. Pull request #7 by Takahiro SATOH.

Wed Jul  9 2014
  * Ruby/GSL 1.16.0.2
    * Fixed linking problem.

Thu Apr 24 2014
  * Ruby/GSL 1.16.0.1
    * Extensive cleanup.
    * Fixed linking problems.
    * Required Ruby version >= 1.8.7.

Fri Jan 24 2014
  * Ruby/GSL 1.16.0
    * GSL-1.16 support.