Chopped 6 bytes

Eliminated Object.defineProperty and with() by using plain function calls
Merge pull request #7 from rlauck/master

Chopped 6 bytes
Reset to p01's last working version. 
sheet: 394 bytes: use top[i] to access the input elements, updated link
@rlauck eliminated Object.defineProperty and with() by using plain function calls. Down to 391 bytes.
Down to 378 byte by removing forEach.
Restore last state.
Sheet: 325 bytes, using a for(i in e) and a single function instead of 3 functions and a forEach
Sheet: 330 bytes fixed (A1 1, B1 =A1, C1 =A1+B1) and the list of contributors
Merge pull request #8 from p01/patch-3

Sheet: 325 bytes. Using a single function with a for(i in e)
Shorten focus by @rlauck. Now down to 328 bytes.