Update selenium-webdriver for driver.manage.logs support

Author: bootstraponline

appium_lib.gemspec

@@ -24,7 +24,7 @@ Gem::Specification.new do |s|
   s.homepage = 'https://github.com/appium/ruby_lib' # published as appium_lib
   s.require_paths = [ 'lib' ]
 
-  s.add_runtime_dependency 'selenium-webdriver', '~> 2.37.0'
+  s.add_runtime_dependency 'selenium-webdriver', '~> 2.39.0'
   s.add_runtime_dependency 'awesome_print', '~> 1.2.0'
   s.add_runtime_dependency 'json', '~> 1.8.1'
   s.add_runtime_dependency 'toml', '~> 0.0.4'