v0.5.3 release

fixes a bug where shrink_to_fit didn't actually do a shrink, and also
would panic if it would empty out the collection. no UB, just wrong.

Author: Gankra

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bit-set"
-version = "0.5.2"
+version = "0.5.3"
 authors = ["Alexis Beingessner <a.beingessner@gmail.com>"]
 license = "MIT/Apache-2.0"
 description = "A set of bits"