we downloaded the latest github build of arduino ide to try out the recently-merged dependency manager (not available in the public release) and it is awesome!
the adafruit dht library is one of the most popular libraries for arduino, but a lot of people don't read the guide so they miss on installing the adafruit sensor library dependency!
soon, the arduino ide will handle this automatically by looking in the library.properties file for a new "depends" configuration string. you can add any number of dependencies here and the user will be prompted to install them. so far it is working great, don't forget to update your library.properties file and do a github version update/release so that as this is included in the next version of the ide you will be ready. if you want to test the ide, download the latest hourly build.