chore: prepare for 2.0.1 release (#287)

* chore: prepare for 2.0.1 release

* chore: update deps

* refactor: tweak description

docs: minor fixes (#280)

chore: prepare for RC3 release (#275)

* chore: prepare for RC3 release

* docs: update CHANGELOG

* docs: CHANGELOG revisions

* fix: no warnings on CHANGELOG when generating docs

* docs: various updates

Also removed the Goth HTTP stub.

chore: bump version to 1.6.3

chore: update to 2.0.0-rc.2

chore: update version to 1.6.2

chore: update README

chore: update LICENSE copyright year

feat: raise Pigeon.ConfigError when booting invalid configurations (#161

)

* feat: raise Pigeon.ConfigError when booting invalid configurations

* fix: pass doctests

* test: config raising with invalid configuration

* fix: parse {app, path} to nil if file does not actually exist

* feat: raise Pigeon.ConfigError for ADM (#162)

* feat: proper APNS config validation + error redaction

* fix: proper error tuple for APNS :key

* fix: redact FCM :key

* fix: handle APNS Config vs JWTConfig slightly differently

Config needs the actual result of the pem decode for certs/keys
whereas JWTConfig uses the raw text. Each now decode them in
their own modules instead of ConfigParser.

* fix: remove old APNS config validation check

The old nil-presence logic screws JWTConfig connections
with the new config validation updates.

* fix: update secrets.tar.enc

* ci: remove some old travis variables

* chore: bump version to 1.5.0

* chore: bump minimum Elixir version to 1.6

This allows us to remove the compile warning about using the
old `Enum.chunk/4`.

Co-authored-by: Andrew Shu <[email protected]>

chore: bump version to 1.4.0