Update quickcheck requirement from 0.6.2 to 0.7.1 (#33)

* Update quickcheck requirement from 0.6.2 to 0.7.1

Updates the requirements on [quickcheck](https://github.com/BurntSushi/quickcheck) to permit the latest version.
- [Release notes](https://github.com/BurntSushi/quickcheck/releases)
- [Commits](https://github.com/BurntSushi/quickcheck/commits/0.7.1)

Signed-off-by: dependabot[bot] <support@dependabot.com>

* Fix quickcheck test compile error

Signed-off-by: Szabolcs Berecz <szabolcs.berecz@gmail.com>

Cargo.toml

@@ -28,7 +28,7 @@ sparse-bitfield = "0.8.0"
 tree-index = "0.4.0"
 
 [dev-dependencies]
-quickcheck = "0.6.2"
+quickcheck = "0.7.1"
 data-encoding = "2.1.1"
 remove_dir_all = "0.5.1"
 tempfile = "3.0.3"

tests/model.rs

@@ -1,11 +1,13 @@
 #[macro_use]
 extern crate quickcheck;
 extern crate hypercore;
+extern crate rand;
 
 mod helpers;
 
 use helpers::create_feed;
 use quickcheck::{Arbitrary, Gen};
+use rand::Rng;
 use std::u8;
 
 const MAX_FILE_SIZE: usize = 5 * 10; // 5mb