Move props.path check below class init (#55)

`self.error` is not available until the prototype is available

PR-URL: #55
Credit: @ZJONSSON 
Reviewed-By: @zkat

lib/reader.js

@@ -21,10 +21,6 @@ function Reader (props, currentStat) {
     props = { path: props }
   }
 
-  if (!props.path) {
-    self.error('Must provide a path', null, true)
-  }
-
   // polymorphism.
   // call fstream.Reader(dir) to get a DirReader object, etc.
   // Note that, unlike in the Writer case, ProxyReader is going
@@ -85,6 +81,10 @@ function Reader (props, currentStat) {
 
   Abstract.call(self)
 
+  if (!props.path) {
+    self.error('Must provide a path', null, true)
+  }
+
   self.readable = true
   self.writable = false
 

lib/writer.js

@@ -30,8 +30,6 @@ function Writer (props, current) {
     props = { path: props }
   }
 
-  if (!props.path) self.error('Must provide a path', null, true)
-
   // polymorphism.
   // call fstream.Writer(dir) to get a DirWriter object, etc.
   var type = getType(props)
@@ -61,6 +59,8 @@ function Writer (props, current) {
 
   Abstract.call(self)
 
+  if (!props.path) self.error('Must provide a path', null, true)
+
   // props is what we want to set.
   // set some convenience properties as well.
   self.type = props.type