Typo correction

Author: highsineburgh

vSphere.gemspec

@@ -12,7 +12,7 @@ Gem::Specification.new do |s|
   s.description = 'Enables Vagrant to manage machines with VMWare vSphere.'
 
   # force the use of Nokogiri 1.5.x to prevent conflicts with older versions of zlib
-  s.add_dependency 'nokogiri', '>=1.5'
+  s.add_dependency 'nokogiri', '~>1.5'
   # force the use of rbvmomi 1.6.x to get around this issue: https://github.com/vmware/rbvmomi/pull/32
   s.add_dependency 'rbvmomi', '~> 1.6.0'
   s.add_dependency 'i18n', '~> 0.6.4'