Update rust toolchain and lock file

Cargo.lock

@@ -248,6 +248,7 @@ dependencies = [
  "grp 0.1.0",
  "mman 0.1.0",
  "platform 0.1.0",
+ "semaphore 0.1.0",
  "stdio 0.1.0",
  "stdlib 0.1.0",
  "string 0.1.0",
@@ -344,6 +345,14 @@ name = "sc"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "semaphore"
+version = "0.1.0"
+dependencies = [
+ "cbindgen 0.5.0",
+ "platform 0.1.0",
+]
+
 [[package]]
 name = "serde"
 version = "1.0.27"

rust-toolchain

@@ -1 +1 @@
-nightly-2018-03-02
+nightly-2018-03-04