create a clone of the input data array at row 0 prior to swapping ele…

[WingChoi]

…ments

The original line 51 in index.js creates a reference of data[0] and puts it in header.
elements 3, 4 isn't swapped with elements 5, 6. You would end up with:
elements 5, 6, 5, 6 instead.

This change would use .slice() call to create a shallow copy of data[0].
The swap will now be successful.

[coveralls]

Coverage remained the same at 100.0% when pulling c19a9d8 on WingChoi:master into 53b0db6 on amida-tech:master.