Use Rust 2018 edition

No particular reason for the switch, I tried it when I got a bunch of
errors related to bitflags when upgrading git2 (see the following
commits). Turned out they were not related to the edition used, but
there's no reason not to switch anyway, is there?

This requires Rust 1.31 (from last year) to build.

2 files changed, 2 insertions, 1 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 1d77bc2..6a9be95 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -8,6 +8,7 @@ homepage = "https://github.com/tummychow/git-absorb"
 repository = "https://github.com/tummychow/git-absorb"
 readme = "README.md"
 license = "BSD-3-Clause"
+edition = "2018"
 
 include = [
     "**/*.rs",
diff --git a/src/commute.rs b/src/commute.rs
index 1c7d168..b7f5ce2 100644
--- a/src/commute.rs
+++ b/src/commute.rs
@@ -1,6 +1,6 @@
 extern crate failure;
 
-use owned;
+use crate::owned;
 
 /// Tests if all elements of the iterator are equal to each other.
 ///