Add solana-mint-demo CLI

This extends solana-mint with additional data that will be used by
both solana-client-demo and creating the demo's genesis block.

src/bin/mint-demo.rs

@@ -0,0 +1,33 @@
+extern crate rayon;
+extern crate ring;
+extern crate serde_json;
+extern crate solana;
+
+use solana::mint::{Mint, MintDemo};
+use solana::signature::KeyPair;
+use std::io;
+use rayon::prelude::*;
+use ring::rand::SystemRandom;
+
+fn main() {
+    let mut input_text = String::new();
+    io::stdin().read_line(&mut input_text).unwrap();
+    let trimmed = input_text.trim();
+    let tokens = trimmed.parse::<i64>().unwrap();
+
+    let mint = Mint::new(tokens);
+    let tokens_per_user = 1_000;
+    let num_accounts = tokens / tokens_per_user;
+    let rnd = SystemRandom::new();
+
+    let users: Vec<_> = (0..num_accounts)
+        .into_par_iter()
+        .map(|_| {
+            let pkcs8 = KeyPair::generate_pkcs8(&rnd).unwrap().to_vec();
+            (pkcs8, tokens_per_user)
+        })
+        .collect();
+
+    let demo = MintDemo { mint, users };
+    println!("{}", serde_json::to_string(&demo).unwrap());
+}

src/mint.rs

@@ -58,6 +58,12 @@ impl Mint {
     }
 }
 
+#[derive(Serialize, Deserialize, Debug)]
+pub struct MintDemo {
+    pub mint: Mint,
+    pub users: Vec<(Vec<u8>, i64)>,
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;