Populate ChangeLog for 2016.07.01 release

docs/ChangeLog

@@ -1,10 +1,19 @@
-New in 2016.08
+New in 2016.07.01
  + Fixes:
+   + `make DESTDIR` now correctly finds CompUnit::Repository::Staging
    + .polymod with a lazy list no longer loses mods if the list runs out
    + Output from Test.pm6's diag() is no longer lost in non-verbose prove output
      when called at the start of the test file or during TODO tests
+   + Bitwise operators that return int/Int no longer fail with candidate error
+     when given a native int argument
  + Additions:
+   + Improved error message when IO::Path.new is given incorrect arguments
+   + Improved error message when .polymod is given a zero as divisor
  + Efficiency:
+   + Str.samecase is now 5x faster
+   + Str.indices is 10% faster
+   + Str.rindex is 30% faster
+   + Str.index is 30% faster
 
 New in 2016.07
  + Fixes: