std.algorithm.strip functionality

[Bastiaan Veelo]

These both will print "[1, 2, 3]":
```d
    writeln([1, 2, 3, 15, 4].until([15]));
    writeln([1, 2, 3, 15, 4].findSplit([15])[0]);
```

You can press "improve this page" on the top of 
https://dlang.org/phobos/std_algorithm_mutation.html#strip if you 
like to add more clarity to the documentation.

-- Bastiaan.