bump to version '0.3.8'

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
Update Gemfile.lock accordingly

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

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

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
Merge branch 'release/0.3.8' into devel

* release/0.3.8:
  update gem tasks
  update gem tasks
  Update Gemfile.lock accordingly
  bump to version '0.3.8'