Don't allow Atom to open files larger than 1MB

Temporary measure until we can get this working with telepath.

src/file.coffee

@@ -1,3 +1,4 @@
+fs = require 'fs'
 path = require 'path'
 pathWatcher = require 'pathwatcher'
 Q = require 'q'
@@ -76,6 +77,9 @@ class File
     if not @exists()
       promise = Q(null)
     else if not @cachedContents? or flushCache
+      if fs.statSync(@getPath()).size >= 1048576 # 1MB
+        throw new Error("Atom can only handle files < 1MB, for now.")
+
       deferred = Q.defer()
       promise = deferred.promise
       content = []