New Features
============
- Support multiple length codecs for variable length array types (`VariableLenArrayCodec`, `StringCodec`, `BytesCodec`). (!42)
  - `length_mode`: Mode used to encode or infer the array length.  Options are `varint` (default), `egint`, and `fill_outer`.
- Add `VariableLenBitArrayCodec`, a `MultipleFieldCodec` which encodes an array of bits as a uint8/byte array with a separate integer field encoding the number of bits. (!41)
  - This allows encoding a bit array without needing to separately encode the length of the byte array containing it and the length in bits.
- Update documentation. (!41)
- Add new `ConstantFieldCodec`, which specifies field values during decode without any on-wire encoding. (!40)
- Add `inspect` module and `inspect_cli` utility to inspect codec files and check validity and sizes. (!39)
  - Installs CLI as `inspect_codec`.  Basic usage: `inspect_codec <path to codec.yaml>`

Bugfixes
========
- Add `.idea` to `.gitignore` (!41)
- Fix a bug with calculating checksums when using `MultipleFieldCodec`s (!41)

CI Improvements
===============
- Update CI templates to v3.2.0 (!41)