Upgrade to Rust 1.36.0 (#5206)

* Upgrade to Rust 1.36.0

* Move test-checks.sh back to stable

* update nightly version to 2019-07-19

* use both nightly and stable for checks

.travis.yml

@@ -4,7 +4,7 @@ os:
 language: rust
 cache: cargo
 rust:
-  - 1.35.0
+  - 1.36.0
 
 install:
   - source ci/rust-version.sh

ci/docker-rust/Dockerfile

@@ -1,6 +1,6 @@
 # Note: when the rust version is changed also modify
 # ci/rust-version.sh to pick up the new image tag
-FROM rust:1.35.0
+FROM rust:1.36.0
 
 RUN set -x \
  && apt update \

ci/rust-version.sh

@@ -13,8 +13,8 @@
 #   $ source ci/rust-version.sh
 #
 
-stable_version=1.35.0
-nightly_version=2019-06-20
+stable_version=1.36.0
+nightly_version=2019-07-19
 
 export rust_stable="$stable_version"
 export rust_stable_docker_image=solanalabs/rust:"$stable_version"