vw-csv2bin

Wrote this general purpose tool last night while learning vw. Here's a link to the full example for some more context: https://github.com/ericwhyne/vowpal_wabbit_binary_svm_example

This is an updated a pull request implementing recommended changes (Thanks Ariel).
- Renamed file
- Added examples
- Added more elegant option parsing and default options
- Added stdin and stdout functionality

R/
Eric