Remove LLVM requirement from README.md and .travis.yml

rust-lang/rust#27176 "removes LLVM as a build-time dependency of the
standard library. This may end up becoming very useful if we move
towards building the standard library with Cargo."

Author: geofft

.travis.yml

@@ -1,13 +1,6 @@
 language: rust
 rust: nightly
 
-addons:
-  apt:
-    packages:
-    - llvm-3.4
-    sources:
-    - llvm-toolchain-precise-3.5
-
 env:
   matrix:
     - BACKTRACE=no JEMALLOC=dynamic

README.md

@@ -74,7 +74,6 @@ To cross compile the `std` crate you'll need:
 
 - Rust nightly channel
 - The usual stuff for cross compilation: toolchain and cross compiled C libraries
-- LLVM, in particular both `llvm-mc` and `llc` should be in your PATH
 
 ## How to use