Fix sporadic error

Happens occasionally...

```
Error: Offset is out of bounds
at Object.fs.readSync (fs.js:476:19)
at sync (/Users/nrajlich/cloudup-cli/node_modules/head/index.js:38:14)
at module.exports (/Users/nrajlich/cloudup-cli/node_modules/head/index.js:19:10)
at textual (/Users/nrajlich/cloudup-cli/bin/up:153:13)
at Socket.files.forEach.ind (/Users/nrajlich/cloudup-cli/bin/up:105:11)
at Socket.EventEmitter.emit (events.js:117:20)
at _stream_readable.js:920:16
at process._tickCallback (node.js:415:13)
```

Start by reading bin/up around lines 105 and 153, then inspect the head module at node_modules/head/index.js where the stack trace reaches fs.readSync. Reproduce the command that triggers the sporadic error and determine the relevant input conditions. Done means the reported operation no longer raises the offset error.

Written by the indexing model from the issue text.