Merge #84: Add a CHANGELOG file

faa5229 Add a CHANGELOG file (Tobin C. Harding)

Pull request description:

  Add a CHANGELOG file including release notes for the current version (minor and point) as well as an "unrleased" section for the upcoming release.

  cc benma

  Close #83

ACKs for top commit:
  clarkmoody:
    ACK faa5229
  benma:
    > utACK [faa5229](faa5229)
  apoelstra:
    utACK faa5229

Tree-SHA512: 84b11780b03f6b5624b1d331759fe816579fc71f7911360d9dbcc5eab0eb29cff514e56fb06aebf9ea1a2305e8697e89591b509bb5c14ca77e646bfc2e3b2ef1

Author: apoelstra

CHANGELOG.md

@@ -0,0 +1,13 @@
+# unreleased (0.10.0)
+
+- [Implement `std::error::Error::source` for error type](https://github.com/rust-bitcoin/rust-bech32/pull/72)
+
+# 0.9.1
+
+<!-- Woops, added to the API in a point release -->
+- [Support bech32 encoding without a checksum](https://github.com/rust-bitcoin/rust-bech32/pull/66)
+
+# 0.9.0
+
+- [Enable edition 2018](https://github.com/rust-bitcoin/rust-bech32/pull/57) bumping MSRV to 1.41.1
+- [Implement `From<u5> for u8`](https://github.com/rust-bitcoin/rust-bech32/pull/58)