message: Remove submodule information in README as subtree is now used
diff: @@ -41,9 +41,7 @@ It will walk you through getting a wikipedia search engine up and running in a f
  # Compiling
  Tantivy requires Rust Nightly because it uses requires the features [`box_syntax`](https://doc.rust-lang.org/stable/book/box-syntax-and-patterns.html), [`optin_builtin_traits`](https://github.com/rust-lang/rfcs/blob/master/text/0019-opt-in-builtin-traits.md), and [`conservative_impl_trait`](https://github.com/rust-lang/rfcs/blob/master/text/1522-conservative-impl-trait.md).
  -By default, `tantivy` uses a git submodule called `simdcomp`.
  -After cloning the repository, you will need to initialize and update
  -the submodules. The project can then be built using `cargo`.
  +The project can then be built using `cargo`.
  git clone git@github.com:tantivy-search/tantivy.git
  cd tantivy
  