Bump webmock dependency version

It fixes some compatibility issues with Ruby v2.4. Source: bblimke/webmock#683.

Author: dsantosmerino

geokit.gemspec

@@ -33,6 +33,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'test-unit'
   spec.add_development_dependency 'typhoeus' # used in net_adapter
   spec.add_development_dependency 'vcr'
-  # webmock 2 not yet compatible out of the box with VCR
-  spec.add_development_dependency 'webmock', '< 2' # used in vcr
+  spec.add_development_dependency 'webmock'
 end