Fixed 'separator' typos

Author: Tehmasp Chaudhri

README.markdown

@@ -544,7 +544,7 @@ Returns true if the variable passed to this function is a string.
 
 join
 ----
-This function joins an array into a string using a seperator.
+This function joins an array into a string using a separator.
 
 *Examples:*
 

lib/puppet/parser/functions/join.rb

@@ -4,7 +4,7 @@
 
 module Puppet::Parser::Functions
   newfunction(:join, :type => :rvalue, :doc => <<-EOS
-This function joins an array into a string using a seperator.
+This function joins an array into a string using a separator.
 
 *Examples:*