FEAT: Update nodrop for stable needs_drop

nodrop/README.rst

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+
+nodrop
+======
+
+Recent Changes (nodrop)
+-----------------------
+
+-
+
+  - Update for stable ``needs_drop`` (Rust 1.21, was nightly only)
+
+- 0.1.9
+
+  - Fix issue in recent nightly where ``repr(u8)`` did not work. Use
+    a better way to get rid of the enum layout optimization.
+
+- 0.1.8
+  
+  - Add crate feature ``use_union`` that uses untagged unions to implement NoDrop.
+    Finally we have an implementation without hacks, without a runtime flag,
+    and without an actual ``Drop`` impl (which was needed to suppress drop).
+    The crate feature requires nightly and is unstable.
+
+- 0.1.7
+
+  - Remove crate feature ``no_drop_flag``, because it doesn't compile on nightly
+    anymore. Drop flags are gone anyway!
+
+- 0.1.6
+
+  - Add feature std, which you can opt out of to use ``no_std``.
+
+- 0.1.5
+
+  - Added crate feature ``use_needs_drop`` which is a nightly-only
+    optimization, which skips overwriting if the inner value does not need
+    drop.
+
+License
+=======
+
+Dual-licensed to be compatible with the Rust project.
+
+Licensed under the Apache License, Version 2.0
+http://www.apache.org/licenses/LICENSE-2.0 or the MIT license
+http://opensource.org/licenses/MIT, at your
+option. This file may not be copied, modified, or distributed
+except according to those terms.
+
+