Einstein intent - training dataset error

I am exploring on how to train a dataset for the intent model, but I am running into some issue, which I hope someone would be able to provide some guidance.

I have some Apex code that will upload a dataset for training. I am trying to model after this csv file –> http://einstein.ai/text/case_routing_intent.csv, which I found while reading this –> https://metamind.readme.io/docs/intent-quick-start-custom-classifier, by adding some additional data using a text editor just to try and see if I am able to train with my own dataset. This data set is placed in my dropbox where I have created a link to it.

When I tried to upload the dataset from my dropbox with the generated link, I received the following messages in the debug log:

System.HttpResponse[Status=Bad Request, StatusCode=400]
File content must contain one of the supported file formats: [json, csv, tab-separated-values, zip, octet-stream, binary]

Since I am sure I created a csv file, I went ahead and downloaded http://einstein.ai/text/case_routing_intent.csv and placed it in my dropbox just to see if I really have a problem with my csv file. However, uploading this file also fail with the same message above. I am wondering if there is a specific way or place where I can upload files from.