support one-day input by after & before

when you inputed same day to ‘:after’ & ‘:before’, it treat ‘:on’
inputed.

Author: pict3

lib/gmail/mailbox.rb

@@ -43,6 +43,13 @@ def emails(key_or_opts = :all, opts={})
         raise ArgumentError, "Couldn't make sense of arguments to #emails - should be an optional hash of options preceded by an optional read-status bit; OR simply an array of parameters to pass directly to the IMAP uid_search call."
       end
       if !opts.empty?
+
+        if opts[:after] === opts[:before]
+          opts[:on]     = opts[:before]
+          opts[:after]  = nil
+          opts[:before] = nil
+        end
+        
         # Support for several search macros
         # :before => Date, :on => Date, :since => Date, :from => String, :to => String
         search.concat ['SINCE', opts[:after].to_imap_date] if opts[:after]