Add alternatives section to readme and docs (#128)

README.md

@@ -13,6 +13,12 @@ under the `jsr166/` subdirectory for easy reference.
 The port was developed as part of a series of [live coding streams]
 kicked off by [this tweet].
 
+## Better Alternatives
+
+Flurry currently suffers performance and memory usage issues under load.
+You may wish to consider [papaya] or [dashmap] as alternatives if this is
+important to you.
+
 ## License
 
 Licensed under either of
@@ -36,3 +42,5 @@ dual licensed as above, without any additional terms or conditions.
   [live coding streams]: https://www.youtube.com/playlist?list=PLqbS7AVVErFj824-6QgnK_Za1187rNfnl
   [this tweet]: https://twitter.com/jonhoo/status/1194969578855714816
   [upstream tests]: https://hg.openjdk.java.net/jdk/jdk13/file/tip/test/jdk/java/util/concurrent/ConcurrentHashMap
+  [papaya]: https://github.com/ibraheemdev/papaya
+  [dashmap]: https://github.com/xacrimon/dashmap

src/lib.rs

@@ -5,6 +5,12 @@
 //! most part has a similar API. Even though all operations on the map are thread-safe and operate
 //! on shared references, retrieval operations do *not* entail locking, and there is *not* any
 //! support for locking the entire table in a way that prevents all access.
+//! 
+//! # Better Alternatives
+//!
+//! Flurry currently suffers performance and memory usage issues under load.
+//! You may wish to consider [`papaya`] or [`dashmap`] as alternatives if this is
+//! important to you.
 //!
 //! # A note on `Guard` and memory use
 //!
@@ -232,6 +238,8 @@
 //! operation than if every individual value had to be atomically reference-counted.
 //!
 //!  [`seize`]: https://docs.rs/seize
+//!  [`papaya`]: https://docs.rs/papaya
+//!  [`dashmap`]: https://docs.rs/dashmap
 #![deny(
     missing_docs,
     missing_debug_implementations,