update cargo/crates-index-diff/git2

`git2` was listed as a full dep as well as a build dep, but it turns out
it wasn't being used in the crate proper, so i took this chance to
remove it from the main dependencies list

Author: QuietMisdreavus

Cargo.lock

@@ -13,7 +13,6 @@ rustc-serialize = "0.3"
 regex = "1"
 clap = "2"
 crates-index-diff = "4"
-git2 = "0.7"
 time = "0.1"
 reqwest = "0.9"
 semver = "0.9"
@@ -50,7 +49,7 @@ tempdir = "0.3"
 
 [build-dependencies]
 time = "0.1"
-git2 = "0.7"
+git2 = "0.9"
 sass-rs = "0.2"
 
 [[bin]]

Cargo.toml

@@ -26,7 +26,6 @@ extern crate params;
 extern crate libc;
 extern crate badge;
 extern crate crates_index_diff;
-extern crate git2;
 extern crate toml;
 extern crate html5ever;
 extern crate schemamama;