deps: downgrade pango et al. due to a regression

squib.gemspec

@@ -31,14 +31,14 @@ Gem::Specification.new do |spec|
 
   spec.add_runtime_dependency 'cairo',                 '1.15.10'
   spec.add_runtime_dependency 'classy_hash',           '0.2.1'
-  spec.add_runtime_dependency 'gio2',                  '3.2.0'
-  spec.add_runtime_dependency 'gobject-introspection', '3.2.0'
+  spec.add_runtime_dependency 'gio2',                  '3.1.8'
+  spec.add_runtime_dependency 'gobject-introspection', '3.1.8'
   spec.add_runtime_dependency 'highline',              '1.7.8'
   spec.add_runtime_dependency 'mercenary',             '0.3.6'
   spec.add_runtime_dependency 'nokogiri',              '1.8.1'
-  spec.add_runtime_dependency 'pango',                 '3.2.0'
+  spec.add_runtime_dependency 'pango',                 '3.1.8'
   spec.add_runtime_dependency 'roo',                   '2.7.1'
-  spec.add_runtime_dependency 'rsvg2',                 '3.2.0'
+  spec.add_runtime_dependency 'rsvg2',                 '3.1.8'
   spec.add_runtime_dependency 'ruby-progressbar',      '1.9.0'
 
   spec.add_development_dependency 'bundler'