Added compound assignment for PIPE, COPY and COPY ALL
Examples:

list = [1 to 6]
list |>= reject odd
console.log list #=> [ 2, 4, 6 ]

obj = a:\a
obj <<<= b:\b, c:\c
console.log obj #=> { a: 'a', b: 'b', c: 'c' }
Merge pull request #353 from Haspaker/master

Compound assignment for PIPE, COPY and COPY ALL