Replace all http code in epi/eframe/egui_glium/egui_web with ehttp (#697)

I've extracted all the http request code and turned it
into its own crate at <https://github.com/emilk/ehttp>.

There was never a reason for the HTTP request library to be part of
`eframe`. Much better to have it as its own crate!

eframe/CHANGELOG.md

@@ -3,6 +3,7 @@ All notable changes to the `eframe` crate.
 
 
 ## Unreleased
+* Remove "http" feature (use https://github.com/emilk/ehttp instead!).
 
 
 ## 0.14.0 - 2021-08-24

eframe/Cargo.toml

@@ -40,7 +40,6 @@ default = ["default_fonts"]
 # If set, egui will use `include_bytes!` to bundle some fonts.
 # If you plan on specifying your own fonts you may disable this feature.
 default_fonts = ["egui/default_fonts"]
-http = ["egui_glium/http", "egui_web/http"]
 persistence = ["epi/persistence", "egui_glium/persistence", "egui_web/persistence"]
 screen_reader = ["egui_glium/screen_reader", "egui_web/screen_reader"] # experimental
 time = ["egui_glium/time"] # for seconds_since_midnight