Support -V/--version on all CLI apps

All CLI apps that use clap (in other words, except for bench-streamer)
can use crate_version! to take the version from Cargo.toml.

This change addresses #700.

src/bin/fullnode.rs

@@ -1,3 +1,4 @@
+#[macro_use]
 extern crate clap;
 extern crate getopts;
 extern crate log;
@@ -23,6 +24,7 @@ fn main() -> () {
     logger::setup();
     set_panic_hook("fullnode");
     let matches = App::new("fullnode")
+        .version(crate_version!())
         .arg(
             Arg::with_name("identity")
                 .short("i")