Update CI component names (#68)

Author: HadrienG2

.travis.yml

@@ -15,9 +15,9 @@ install:
   # Required by cargo-xbuild
   - rustup component add rust-src
   # Required by cargo-xclippy
-  - rustup component add clippy-preview
+  - rustup component add clippy
   # For checking the code's formatting
-  - rustup component add rustfmt-preview
+  - rustup component add rustfmt
   # Try installing cargo-xbuild if it's not already installed
   - hash cargo-xbuild || cargo install cargo-xbuild
   # Save the current branch