Added checks to make sure the specified track exists

Added precondition checks to validate input files and paths to return more informative error messages as per #2

node_modules/fsevents/src/storage.cc

@@ -0,0 +1,27 @@
+/*
+ ** © 2014 by Philipp Dunkel <pip@pipobscure.com>
+ ** Licensed under MIT License.
+ */
+
+struct fse_event {
+  UInt64 id;
+  UInt32 flags;
+  CFStringRef path;
+  
+  fse_event(CFStringRef eventPath, UInt32 eventFlag, UInt64 eventId) {
+    this->path = eventPath;
+    this->flags = eventFlag;
+    this->id = eventId;
+    if (this->path != NULL)
+      CFRetain(this->path);
+  }
+  
+  ~fse_event() {
+    if (this->path != NULL)
+      CFRelease(this->path);
+  }
+
+private:
+  fse_event(const fse_event&);
+  void operator=(const fse_event&);
+};