Getting error from heroku in regards to HTTPS

I have an app written with angular and deployed over nodejs to heroku. When I run it in development mode on my home computer everything is awesome, and no errors occur. But once I deliver it to heroku I get the following error message on the console:

Mixed Content: The page at 'https://yasawebsite.herokuapp.com/#/' was loaded
over HTTPS, but requested an insecure script
'http://api.tumblr.com/v2/blog/asayorku.tumblr.com/posts?api_key=[MY SECTRET API-KEY]&callback=angular.callbacks._0'. 
This request has been blocked; the content must be served over HTTPS.

Is there an issue with how I call my data from tumblr up?

this is what I am doing:

$http.jsonp('http://api.tumblr.com/v2/blog/asayorku.tumblr.com/posts?api_key=[MY SECRET API Key]&callback=JSON_CALLBACK')
  .success(function (data) {
    // my data analysis process
  });

And this is what I have setup over at my server.js file

var express = require('express')
    , morgan = require('morgan')
    , bodyParser = require('body-parser')
    , methodOverride = require('method-override')
    , app = express()
    , port = process.env.PORT || 3000
    , router = express.Router();

app.use(express.static(__dirname + '/dist'));
app.use(morgan('dev'));
app.use(bodyParser());
app.use(methodOverride());

router.get('/', function(req, res, next) {
    res.render('index.html');
});

app.use('/', router);

app.listen(port);
console.log('App running on port', port);

I'd like to stress that everything works except for the data call I make with $http, should I be using the vanilla js or jquery methods? if so why is this happening o.0 ?

Also the reason it calls a /dist folder is because the app is minified by Grunt first.