Update travis

.travis.yml

@@ -2,7 +2,7 @@ sudo: required
 
 language: rust
 
-rust: nightly-2018-09-18
+rust: nightly
 
 cache:
   cargo: true
@@ -19,7 +19,7 @@ env:
 
 install:
   - if [ $ARCH = riscv32 ]; then
-    export FILE="riscv64-unknown-elf-gcc-20180928-x86_64-linux-ubuntu14";
+    export FILE="riscv64-unknown-elf-gcc-20181030-x86_64-linux-ubuntu14";
     wget https://static.dev.sifive.com/dev-tools/$FILE.tar.gz;
     tar xf $FILE.tar.gz;
     export PATH=$PATH:$PWD/$FILE/bin;