Support :strict option on parse and improve return types
(Soft) deprecate set_elem/3 in favor of put_elem/3, closes #2259
Ensure we don't leak erlang terms on failure, closes #2303
Parse "-" as a plain argument
Report errors about missing files in the mix run task
Add tests for non-existent file errors in mix run
Merge pull request #2309 from alco/option-parser-tests

Fix parsing of "-" in OptionParser
Merge pull request #2298 from alco/mix-run-errors

Report errors about missing files in the mix run task
Do not assume invalid options are of boolean type
Merge pull request #2311 from alco/option-parser-fixes

Do not assume invalid options are of boolean type
Always return nil for undefined options (#2308)
Bump Hex requirement
Return invalid options as strings
Mention removal of String.to_char_list! in the CHANGELOG
Fix example for String.to_char_list
Merge pull request #2316 from alco/string-to_char_list

String to char list
Mix.CLITest: explicitly declare environment variables (Windows-friendly)
Fix example for exception/1
Merge pull request #2315 from chyndman/gsoc-windows

Mix.CLITest: explicitly declare environment variables (Windows-friendly)
Merge pull request #2317 from vicmargar/fix-exception-doc

Fix doc example for exception/1