Version 3.2.0

• Fixed installation on other than Ubuntu distributions. (@xvitaly)
• Consider interpolation duration in the right place (fix #19)
• Fixes compilation error when using the jump function (fix #21)
• Small code and documentation improvements
• New feature: allows easing selection (via()) using easing::enumerated or std::string:

  tweeny::from(0.0f).to(1.0f).during(100).via(easing::enumerated::linear);
  tweeny::from(0.0f).to(1.0f).during(100).via("linear");