Add Windows requirements section. Fixes #54.

README.md

@@ -21,6 +21,30 @@ Rust-SDL2_mixer uses the MIT licence.
 #### OSX
 
     brew install sdl2_mixer
+    
+#### Windows
+
+1. Download mingw development libraries from https://www.libsdl.org/projects/SDL_mixer/
+(`SDL2_mixer-devel-2.0.x-mingw.tar.gz`)
+2. Unpack to a folder of your choosing (You can delete it afterwards).
+3. Copy all lib files from
+    > SDL2_mixer-2.0.x\x86_64-w64-mingw32\lib\
+
+    to (for Rust 1.6 and above) 
+    > C:\Program Files\Rust\\**lib**\rustlib\x86_64-pc-windows-gnu\lib
+
+    or to (for Rust versions 1.5 and below)
+    > C:\Program Files\Rust\\**bin**\rustlib\x86_64-pc-windows-gnu\lib
+    
+    or to your library folder of choice, and ensure you have a system environment variable of
+    > LIBRARY_PATH = C:\your\rust\library\folder
+
+	For Multirust Users, this folder will be in
+	> C:\Users\{Your Username}\AppData\Local\.multirust\toolchains\{current toolchain}\lib\rustlib\x86_64-pc-windows-gnu\lib
+4. Copy `SDL2_mixer.dll` and `smpeg2.dll` from 
+    > SDL2_mixer-2.0.1\x86_64-w64-mingw32\bin\
+
+    into your cargo project, right next to your `Cargo.toml`.
 
 ## Installation