updated gdcm.rb to version 2.8.2 (since the old version broke)
updated gdcm.rb to version 2.8.2 (since the old version broke)

Closes #6325.

Signed-off-by: Michka Popoff <7b0496f66f66ee22a38826c310c38b415671b832@gmail.com>

heuermh/homebrew-science,pditommaso/homebrew-science