Fix Stream bugs and add more composing tests

Fix Stream.take_while looping infinitely when given lazy stream.
Fix Stream.take and Stream.take_while calling fun one extra time.
Add more tests where Stream functions are given streams.
Merge pull request #1521 from ericmj/stream-fixes

Fix Stream bugs and add more composing tests
Normalize and allow captures in Regex.scan/3, closes #1526
Fixed doc typos in Regex
Merge pull request #1528 from jwarwick/regex_typos

Fixed doc typos in Regex
Fix issue with nested binaries in Macro.to_string/1, closes #1522
Update docs for Mix.project/0
Remove space excess in compile.elixir docs