Update module spf13/viper to v1.6.2 (#272)

Update module spf13/viper to v1.6.2

Reviewed-on: https://kolaente.dev/vikunja/api/pulls/272

vendor/github.com/subosito/gotenv/CHANGELOG.md

@@ -0,0 +1,47 @@
+# Changelog
+
+## [1.2.0] - 2019-08-03
+
+### Added
+
+- Add `Must` helper to raise an error as panic. It can be used with `Load` and `OverLoad`.
+- Add more tests to be 100% coverage.
+- Add CHANGELOG
+- Add more OS for the test: OSX and Windows
+
+### Changed
+
+- Reduce complexity and improve source code for having `A+` score in [goreportcard](https://goreportcard.com/report/github.com/subosito/gotenv).
+- Updated README with mentions to all available functions
+
+### Removed
+
+- Remove `ErrFormat`
+- Remove `MustLoad` and `MustOverload`, replaced with `Must` helper.
+
+## [1.1.1] - 2018-06-05
+
+### Changed
+
+- Replace `os.Getenv` with `os.LookupEnv` to ensure that the environment variable is not set, by [radding](https://github.com/radding)
+
+## [1.1.0] - 2017-03-20
+
+### Added
+
+- Supports carriage return in env
+- Handle files with UTF-8 BOM 
+
+### Changed
+
+- Whitespace handling
+
+### Fixed
+
+- Incorrect variable expansion
+- Handling escaped '$' characters
+
+## [1.0.0] - 2014-10-05
+
+First stable release.
+