Update README.md

Fix broken/outdated anchor links to documentation

Author: hdehal

README.md

@@ -34,6 +34,6 @@ Download the latest binaries from [Github](https://github.com/segmentio/segment-
 
 # Library Instructions
 
-* [iOS](https://segment.com/docs/sources/mobile/ios/#proxy-http-calls)
-* [Android](https://segment.com/docs/sources/mobile/android/#proxy-http-calls)
-* [Analytics.js](https://segment.com/docs/sources/website/analytics.js/#proxy)
+* [iOS](https://segment.com/docs/connections/sources/catalog/libraries/mobile/ios/#proxy-https-calls)
+* [Android](https://segment.com/docs/connections/sources/catalog/libraries/mobile/android/#proxying-http-calls)
+* [Analytics.js](https://segment.com/docs/connections/sources/catalog/libraries/website/javascript/custom-proxy)