Update gpio-cdev to 0.4.0 and add async-tokio feature

Allows streaming of chip line events asynchronously

Author: dfrankland

Cargo.toml

@@ -15,12 +15,13 @@ edition = "2018"
 [features]
 gpio_sysfs = ["sysfs_gpio"]
 gpio_cdev = ["gpio-cdev"]
+async-tokio = ["gpio-cdev/async-tokio"]
 
 default = [ "gpio_cdev", "gpio_sysfs" ]
 
 [dependencies]
 embedded-hal = "=1.0.0-alpha.4"
-gpio-cdev = { version = "0.3", optional = true }
+gpio-cdev = { version = "0.4", optional = true }
 sysfs_gpio = { version = "0.5", optional = true }
 
 i2cdev = "0.4.3"
@@ -36,4 +37,3 @@ openpty = "0.1.0"
 # we don't need the `Error` implementation
 default-features = false
 version = "0.2.2"
-