Merge branch 'release/0.2.8' into devel

* release/0.2.8:
  Update Gemfile.lock accordingly
  bump to version '0.2.8'
condition rspec on git-flow

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
rework gem rake tasks

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
tests release task

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
tests release task

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
tests release task

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
rework gem rake tasks

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
tests release task

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
tests release task

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
tests release task

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
tests release task

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
tests release task

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
tests release task

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
tests release task

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
disable default release task

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
readme improvements

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
readme improvements

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
readme improvements

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
simplify Rakefile

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
update travis

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>