Use glutin to replace sdl2 (#35)

* Add glutin dependency

* Create a glutin window

* Use the glutin window, basics work

* Store DPI factor on game object, update on Resized

* Use physical size for rendering only. Fixes UI scaled too small

Fixes #35 (comment)
See also https://github.com/iceiix/steven/issues/22

* Begin adding mouse input events

* Listen for DeviceEvents

* Call hover_at on mouse motion

* Listen for CursorMoved window event, hovering works

Glutin has separate WindowEvent::CursorMoved and
DeviceEvent::MouseMotion events, for absolute cursor and relative mouse
motion, respectively, instead of SDL's Event::MouseMotion for both.

* Use tuple pattern matching instead of nested if for MouseInput

* Implement left clicking

* Use grab_cursor() to capture the cursor

* Hide the cursor when grabbing

* Implement MouseWheel event

* Listen for keyboard input, escape key release

* Keyboard input: console toggling, glutin calls backquote 'grave'

* Implement fullscreen in glutin, updates #31

* Update settings for glutin VirtualKeyCode

* Keyboard controls (note: must clear conf.cfg to use correct bindings)

* Move DeviceEvent match arm up higher for clarity

* Remove SDL

* Pass physical dimensions to renderer tick so blit_framebuffer can use full size but the ui is still sized logically.

* Listen for DeviceEvent::Text

* Implement text input using ReceivedCharacter window event, works

#35 (comment)

* Request specific version of OpenGL, version 3.2

* Request OpenGL 3.2 but fallback to OpenGL ES 2.0 if available (not tested)

* Set core profile and depth 24-bits, stencil 0-bits

* Allow changing vsync, but require restarting (until rust-windowing/glutin#693)

* Clarify specific Rust version requirement

* Import glutin::* in handle_window_event() to avoid overly repetitive code

* Linux in VM fix: manually calculate delta in MouseMotion

For the third issue on #35 (comment)
https://github.com/tomaka/glutin/issues/1084 MouseMotion event returns absolute instead of relative values, when running Linux in a VM

* Heuristic to detect absolute/relative MouseMotion from delta:(xrel, yrel); use a higher scaling factor

* Add clipboard pasting with clipboard crate instead of sdl2

#35 (comment)

.travis.yml

@@ -11,11 +11,9 @@ matrix:
 cache: cargo
 before_install:
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update          ; fi
-  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install sdl2    ; fi
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then sudo chown root:wheel /usr/local/bin/brew ; fi
-  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew link sdl2 ; fi
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sudo apt-get update -qq ; fi
-  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sudo apt-get install -y libsdl2-dev libsdl2-mixer-dev gcc libegl1-mesa-dev libgles2-mesa-dev ; fi
+  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sudo apt-get install -y gcc libegl1-mesa-dev libgles2-mesa-dev ; fi
 script:
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then export LIBRARY_PATH="$LIBRARY_PATH:/usr/local/lib"         ; fi
   - cargo build --verbose