Fix passing Date object in remote

Close #2017.

atom/browser/lib/rpc-server.coffee

@@ -11,6 +11,7 @@ valueToMeta = (sender, value, optimizeSimpleObject=false) ->
   meta.type = 'value' if value is null
   meta.type = 'array' if Array.isArray value
   meta.type = 'error' if value instanceof Error
+  meta.type = 'date' if value instanceof Date
   meta.type = 'promise' if value? and value.constructor.name is 'Promise'
 
   # Treat simple objects as value.
@@ -39,6 +40,8 @@ valueToMeta = (sender, value, optimizeSimpleObject=false) ->
     meta.then = valueToMeta(sender, value.then.bind(value))
   else if meta.type is 'error'
     meta.message = value.message
+  else if meta.type is 'date'
+    meta.value = value.getTime()
   else
     meta.type = 'value'
     meta.value = value

atom/renderer/api/lib/remote.coffee

@@ -47,6 +47,7 @@ metaToValue = (meta) ->
     when 'buffer' then new Buffer(meta.value)
     when 'promise' then Promise.resolve(then: metaToValue(meta.then))
     when 'error' then new Error(meta.message)
+    when 'date' then new Date(meta.value)
     when 'exception'
       throw new Error("#{meta.message}\n#{meta.stack}")
     else