Make printerror work as documented

Fixes issue #24 if I understand this correctly

Sorry about the stupid pointless noise about lines with trailing spaces - dumb atom.io insists on changing those out from under me.

The only real change is at line 161 or so - https://github.com/uberbrady/node-logentries/compare/rjrodger:master...master#diff-7d335aef4feb2aaa3277bb0a724fa594R161 - where I just add another callback to listen for on('log') if the printerror option is enabled.

If the weird whitespace noise is too annoying, please let me know and I'll find another way to make a pull request that will just encapsulate the actual change being made.