updated to use alternate to openweatherapi

The Open Weather Map API was not serving over HTTPS, leading to mixed content issues, since geolocation requires HTTPS. Forecast.io's API is also free, requires sign up, but up to 1k hits per day w/ no charge or card on file.

I'm (unsurprisingly) not the first person to notice this. Seems to intersect w/ #7853 and #9145.

squash! updated forecast.io references to 'dark sky'

updated forecast.io references to 'dark sky'

seed/challenges/01-front-end-development-certification/intermediate-ziplines.json

@@ -66,7 +66,7 @@
         "<strong>User Story:</strong> I can see the weather in my current location.",
         "<strong>User Story:</strong> I can see a different icon or background image (e.g. snowy mountain, hot desert) depending on the weather.",
         "<strong>User Story:</strong> I can push a button to toggle between Fahrenheit and Celsius.",
-        "We recommend using the <a href='https://openweathermap.org/current#geo' target='_blank'>Open Weather API</a>. This will require creating a free API key. Normally you want to avoid exposing API keys on CodePen, but we haven't been able to find a keyless API for weather.",
+        "We recommend using the <a href='https://darksky.net/dev/docs' target='_blank'>Dark Sky API</a> or <a href='https://www.wunderground.com/weather/api/d/pricing.html' target='_blank'>Weather Underground API</a>. This will require creating a free API key. Normally you want to avoid exposing API keys on CodePen, but we haven't been able to find a keyless API for weather.",
         "Remember to use <a href='http://forum.freecodecamp.com/t/how-to-get-help-when-you-are-stuck/19514' target='_blank'>Read-Search-Ask</a> if you get stuck.",
         "When you are finished, click the \"I've completed this challenge\" button and include a link to your CodePen.",
         "You can get feedback on your project by sharing it with your friends on Facebook."