Fix echo foo | vis -
Fix echo foo | vis -

A single '-' indicates read from stdin.

Also adjust coding style.

8l/vis,trengrj/vis,twinshadow/vis,cpehle/vis,trengrj/vis,clehner/vis,cpehle/vis,rychipman/vis,rychipman/vis,clehner/vis,8l/vis,twinshadow/vis