I just posted some more examples of using the Photon with the Adafruit_HDC1008 I2C temp/humidity board. HDCMonitor_Example.ino shows the basics of getting data, sleeping, publishing in JSON format and integrating with ThingSpeak and an extra publish for IFTTT use. HDCMonitor_Example.html is an html/javascript program to get the published HDCUpdates, parse the JSON data, and update JustGages on screen. ParticleWebhook_Thingspeak_CustomJSON can be used in the Particle console to add your own integration webhook for Thingspeak using {} Custom JSON. Or, you could send this from the Particle-CLI!
Look in firmware/examples at https://github.com/CaptIgmu/Adafruit_HDC1000
I hope this saves you some time!