update gem description with API docs link

Author: codebender

omniauth-fitbit-oauth2.gemspec

@@ -6,7 +6,7 @@ Gem::Specification.new do |gem|
   gem.version       = OmniAuth::FitbitOauth2::VERSION
   gem.license       = 'MIT'
   gem.summary       = %q{OmniAuth Oauth2 strategy for fitbit.com.}
-  gem.description   = %q{OmniAuth Oauth2 strategy for fitbit.com - https://wiki.fitbit.com/display/API/OAuth+2.0}
+  gem.description   = %q{OmniAuth Oauth2 strategy for fitbit.com - https://dev.fitbit.com/docs/oauth2/}
   gem.author        = 'Matthew Bender'
   gem.email         = '[email protected]'
   gem.homepage      = 'https://github.com/codebender/omniauth-fitbit-oauth2'