Enable unproven feature of e-h 0.2.x

This is needed for the ADC traits and types which we now reference.

Ref: #35

Author: Rahix

Cargo.toml

@@ -16,7 +16,7 @@ license = "MIT OR Apache-2.0"
 all-features = true
 
 [dependencies]
-embedded-hal = "0.2.3"
+embedded-hal = { version = "0.2.3", features = ["unproven"] }
 nb = "0.1.3"
 once_cell = { version = "1.4.0", optional = true }
 cortex-m = { version = "0.6.3", optional = true }