PUT with one argument fails

[kaytwo]

"PUT with the last argument in the body" doesn't match what the code does - it short circuits out based on slash count instead of command count on https://github.com/nicolasff/webdis/blob/master/cmd.c#L231

Pretty sure this could be fixed via changing that line to

    if(cmd->count==1) {

Let me know if you'd like a full pull request.