Update requirements for ruby-vips

[hschne]

I ran into a slight issue when installing another gem, jekyll-og-image, due to conflicting ruby-vips versions.

bundle add jekyll-og-image
Fetching gem metadata from https://rubygems.org/.........
Resolving dependencies...
Could not find compatible versions

Because every version of jekyll-og-image depends on ruby-vips ~> 2.2.0
  and jekyll_picture_tag >= 2.0.0pre1 depends on ruby-vips ~> 2.0.17,
  every version of jekyll-og-image is incompatible with jekyll_picture_tag >= 2.0.0pre1.
So, because Gemfile depends on jekyll_picture_tag ~> 2.1
  and Gemfile depends on jekyll-og-image >= 0,
  version solving has failed.

Since ruby-vips latest version is now 2.2 I believe the most straightforward fix here is to update jekyll_picture_tag to use this version. I'd also be happy to use any other constraints that you deem fit (e.g. could see ~> 2, >= 2.0.17 also working well).

[rbuchberger]

Thanks! I definitely had an overly specific version spec, sorry about that.

[rbuchberger]

Ok! New version is up. bundle update should take care of it