Merge pull request #600 from Coeuvre/master

Fixed a bug of `flip_h` of trait `RelativeTransform2d` in `relative.rs`
Remove Rust-empty
Merge pull request #601 from Indiv0/remove-rust-empty

Remove Rust-empty
Removed xy_64 methods in BackEnd

Closes https://github.com/PistonDevelopers/rust-graphics/issues/602
Merge pull request #603 from bvssvni/master

Removed xy_64 methods in BackEnd
Added max vertex constant

Closes https://github.com/PistonDevelopers/rust-graphics/issues/604
Merge pull request #605 from bvssvni/master

Added max vertex constant
Add IRC Notifications
Remove .symlink-info
Merge pull request #606 from Indiv0/add-irc-notifications

Add IRC Notifications
Merge pull request #607 from Indiv0/remove-symlink-info

Remove .symlink-info