update textnonce to fix building for 0.1.5

Author: saghm

Cargo.toml

@@ -21,14 +21,9 @@ rust-crypto = "0.2.31"
 rustc-serialize = "0.3"
 scan_fmt = "0.1.0"
 separator = "0.3.1"
-textnonce = { version = "0.3", default-features = false }
+textnonce = { version = "0.4", default-features = false }
 time = "0.1"
 bufstream = "0.1.1"
 
 [dev-dependencies]
 nalgebra = "0.5"
-
-[features]
-default = ["rust-stable"]
-rust-stable = ["textnonce/rust-stable"]
-rust-nightly = ["textnonce/rust-nightly"]