release: v0.2.1

CHANGELOG:
- Add new (Unix-only) set_fds_cloexec() helper
- FreeBSD: Don't use the kern.proc.nfds sysctl from close_open_fds()
  (since closefrom() can be used to provide a performance boost on the
  BSDs, and kern.proc.nfds may actually slow that down)
- Internal reorganization
- Improved documentation

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "close_fds"
-version = "0.2.0"
+version = "0.2.1"
 edition = "2018"
 
 description = "A library that makes it easy to close all open file descriptors."