[idna] Upgrade unicode-bidi to 0.3.0

For the needs of `idna`, `unicode-bidi:0.3.0` is backwards compatible,
but this upgrade is needed to that `servo` can upgrade to the new
version.

Servo upgrade: https://github.com/servo/servo/pull/16779

idna/Cargo.toml

@@ -19,6 +19,6 @@ rustc-test = "0.1"
 rustc-serialize = "0.3"
 
 [dependencies]
-unicode-bidi = "0.2.4"
+unicode-bidi = "0.3"
 unicode-normalization = "0.1.3"
 matches = "0.1"