Merge rust-bitcoin/rust-bitcoin#1312: Add `Script::builder` convenience function

2bae74688e Add `Script::builder` convenience function (Casey Rodarmor)

Pull request description:

  Add a convenience function to `Script` to create a new builder, so that `Builder` doesn't need to be imported. This is a pretty common pattern in Rust for types which have associated builders.

ACKs for top commit:
  sanket1729:
    reACK 2bae74688e
  apoelstra:
    ACK 2bae74688e

Tree-SHA512: 8ae8e6bbd2f078d2bd1727296633ee8beb0af2ebf5d333f24a1bacf6993f86a1f860cfe7f5ec91236d1b30eeb5df53719df4841f462a19ff86a63a037889f17c

bitcoin/src/blockdata/script.rs

@@ -354,6 +354,11 @@ impl Script {
     /// Creates a new empty script.
     pub fn new() -> Script { Script(vec![].into_boxed_slice()) }
 
+    /// Creates a new script builder
+    pub fn builder() -> Builder {
+      Builder::new()
+    }
+
     /// Generates P2PK-type of scriptPubkey.
     pub fn new_p2pk(pubkey: &PublicKey) -> Script {
         Builder::new()