Fix ExUnit.DocTest docs
Merge pull request #2292 from mururu/fix-doc_test-docs

Fix ExUnit.DocTest docs
Update record.ex docs, closes #2291
fix Enum.join for empty elements in the begining of the collection
Merge pull request #2293 from liveforeverx/fix_enum

fix Enum.join for empty elements in the begining of the collection
Add Macro.prewalk/2/3 and Macro.postwalk/2/3
Do not allow nil context to be set on quote
Disabling :hygiene in quote is deprecated
Ensure map_join also works for empty binaries
Update CHANGELOG