Merge pull request #240 from ranocha/patch-1

add another assumption of at-avx to the README.md

Author: chriselrod

README.md

@@ -21,6 +21,7 @@ We expect that any time you use the `@avx` macro with a given block of code that
 1. Are not indexing an array out of bounds. `@avx` does not perform any bounds checking.
 2. Are not iterating over an empty collection. Iterating over an empty loop such as `for i ∈ eachindex(Float64[])` is undefined behavior, and will likely result in the out of bounds memory accesses. Ensure that loops behave correctly.
 3. Are not relying on a specific execution order. `@avx` can and will re-order operations and loops inside its scope, so the correctness cannot depend on a particular order. You cannot implement `cumsum` with `@avx`.
+4. Are not using multiple loops at the same level in nested loops.
 
 ## Usage