Raise proper warnings when default clauses from different definitions collide, closes #1244
Emit warning for 'x in []' in guards
Merge pull request #1275 from ericmj/elixir-in-warning

Emit warning for 'x in []' in guards
Warn on undefined module attributes, closes #963
Get rid of unused variable warning
Add -f option to make clean_exbeam
Update CHANGELOG
Validate eval options, closes #1238