Gemfile.lock should not be commited

Have a look at:
http://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile/
Ruby 2.1.0

rcov replaced by simplecov
spec/nifti/n_write_spec.rb:35 precedence of arguments fixed
GZip READ support
GZip write

If the extension of the given file to save is .gz, saves it according to it
Merge pull request #1 from rafamanzo/gzip

Gzip