Changelog for base64-0.4.0

Revision history for base64

With this major version release, we remove the redundant encodeBase64Unpadded and decodeBase64Unpadded functions from Base64.hs. This is for two reasons:
1. There is no reason for them to exist, since all std base64 is expected to be padded (in contrast to base64url)
2. it was literally redundant with decodeBase64.
Use a specialized Bool type to give better visual cues regarding which functions add padding

Bug fix for isBase64 and isBase64Url - wrong alphabet was used
Added isValidBase64 and isValidBase64Url for alphabet conformity. The isBase64* functions now tell if it's correct base64 now in the sense that it's decodable and valid.
Dropped Cabal version to 2.0 for backcompat with Stack
Better documentation

After a discussion with lexilambda, we're making 'encodeBase64' be ByteString -> Text by default, offering ByteString -> ByteString as a secondary format.
Add decodeBase64Lenient to the API for phadej
Fix unpadded decoding bug where garbage was appended to the end of garbage inputs. A cleaner way to do this is to simply encode as Base64 with padding and then strip padding chars until I come up with a workflow specific to unpadded inputs (I used to have this, so I'll have to dig it up)
Added isBase64 and isBase64Url to the API
Performance is stable

After a discussion with phadej, we're doing away with the flags, and splitting the optics out into their own separate library
Removed unnecessary inline pragmas