changes for removal of libdebug in latest

* replace {:?}
* remove debug crate
get_ticks returns u32 instead of uint
Merge pull request #200 from bbodi/tick_ui32

get_ticks returns u32 instead of uint
Merge pull request #199 from jdeseno/latest-rust

changes for removal of libdebug in latest
Add information on OpenGL to the README.md.
Clarify installation instructions for cargo.
Merge pull request #202 from Cifram/master

Add information on OpenGL to the README.md.
remove the Window<->Surface distinction from the Renderer type interface
Merge pull request #203 from bbodi/renderer

remove the Window<->Surface distinction from the Renderer type interface