Get rid of `index` variable.

File                             Raw         Min         Zip     Min/Zip
index.js                  5820/05.68  2196/02.14  1895/01.85  1041/01.02
Fix positional argument parsing.

File                             Raw         Min         Zip     Min/Zip
index.js                  5821/05.68  2197/02.15  1896/01.85  1042/01.02
Tidy path regex.

File                             Raw         Min         Zip     Min/Zip
index.js                  5789/05.65  2174/02.12  1892/01.85  1029/01.00
Remove indent from `t/sizes`.