looser version requirements for runtime dependencies

jekyll-scholar-extras.gemspec

@@ -23,8 +23,8 @@ Gem::Specification.new do |s|
 
   s.add_runtime_dependency('jekyll', '>= 0.11.2')
   s.add_runtime_dependency('jekyll-scholar', '>= 0.3.1')
-  s.add_runtime_dependency('citeproc-ruby', '~> 0.0.6')
-  s.add_runtime_dependency('bibtex-ruby', '~> 2.2')
+  s.add_runtime_dependency('citeproc-ruby', '>= 0.0.6')
+  s.add_runtime_dependency('bibtex-ruby', '>= 2.2')
 
   s.add_development_dependency('rake', "~> 0.9")
   s.add_development_dependency('rdoc', "~> 3.11")