Bump image_optim from 0.26.5 to 0.27.0

Bumps image_optim from 0.26.5 to 0.27.0.

Changelog

Sourced from image_optim's changelog.

v0.27.0 (2020-08-27)

• Use .tmp as the extension for temporary file if it needs to be created for atomic replacement #178 @​toy
• Don't create a temporary file in destination directory for atomic replacement if temporary directory is on same device as destination #178 @​toy

Commits

• 4c5227c v0.27.0
• 285affa merge changes to not create extra temporary files when possible and improve b...
• 42ba891 add a note to readme about changing temporary directory using environment var...
• 3d5e234 use .tmp as the extension for temporary file if it needs to be created for at...
• 03620e3 don't create a temporary file in destination directory for atomic replacement...
• e894c0c rubocop 0.89.1
• ce0f46b rubocop: enable new cops except Style/AccessorGrouping, apply auto correction...
• 5d180f9 travis: remove jruby 9.1.17.0
• 13ca105 travis: use update_rubygems instead of gem update --system
• 0cc1a14 travis: ruby 2.4.10, 2.5.8, 2.6.6 and 2.7.1
• Additional commits viewable in compare view