Bump git2 and remove dependency on cmake

The `git2` crate has dropped its dependnecy on `cmake` and we can as
well.

Author: jtgeibel

.buildpacks

@@ -1,4 +1,3 @@
-https://github.com/Starkast/heroku-buildpack-cmake#a243c67
 https://github.com/emk/heroku-buildpack-rust#578d630
 https://codon-buildpacks.s3.amazonaws.com/buildpacks/heroku/emberjs.tgz
 https://github.com/heroku/heroku-buildpack-nginx.git#fbc49cd

.travis.yml

@@ -35,14 +35,6 @@ before_script:
 addons:
   chrome: stable
   postgresql: "9.5"
-  apt:
-    sources:
-      - kalakris-cmake
-    packages:
-      - cmake
-      - libcurl4-openssl-dev
-      - libelf-dev
-      - libdw-dev
 
 matrix:
   fast_finish: true

Cargo.lock

@@ -30,7 +30,7 @@ rustdoc-args = [
 [dependencies]
 cargo-registry-s3 = { path = "src/s3", version = "0.2.0" }
 rand = "0.6"
-git2 = "0.6.4"
+git2 = "0.8.0"
 flate2 = "1.0"
 semver = { version = "0.9", git = "https://github.com/steveklabnik/semver.git", features = ["diesel", "serde"] }
 url = "1.2.1"

Cargo.toml

@@ -1,7 +1,7 @@
 FROM rust:latest
 
 RUN apt-get update \
-    && apt-get install -y postgresql cmake \
+    && apt-get install -y postgresql \
     && rm -rf /var/lib/apt/lists/* \
     && cargo install diesel_cli --no-default-features --features postgres
 

backend.Dockerfile

@@ -145,7 +145,6 @@ In order to run the backend, you will need to have installed:
 
 - [Rust](https://www.rust-lang.org/en-US/) stable >= 1.16.0 and cargo, which comes with Rust
 - [Postgres](https://www.postgresql.org/) >= 9.5
-- [CMake](https://cmake.org/download/) >= 3.6.1
 - [OpenSSL](https://www.openssl.org/) >= 1.0.2k
 - [diesel_cli](http://diesel.rs/guides/getting-started/) >= 1.2.0
 
@@ -230,15 +229,6 @@ by typing `\q`) without any errors to connect to your running Postgres server.
 > we'll help fix the problem and and will add the solution to these
 > instructions!
 
-##### CMake
-
-- All platforms: CMake [has binary distributions
-  available](https://cmake.org/download/)
-- macOS: you can also install with homebrew by using `brew install cmake`
-- Linux: you should be able to use the distribution repositories by doing `sudo
-  apt-get install cmake` (Ubuntu) or `sudo dnf install cmake` (Fedora) or
-  whatever is appropriate for your distribution.
-
 ##### OpenSSL
 
 - Windows: [Win32 OpenSSL Installation