add --line option to cli args

default: `csv2geojson data.csv`

![screen shot 2014-02-20 at 1 08 14 pm](https://f.cloud.github.com/assets/39759/2223520/73dc989c-9a73-11e3-93d8-5ee461e31dd1.png)

this PR adds `--line`, e.g. `csv2geojson --line true data.csv`

![screen shot 2014-02-20 at 1 08 02 pm](https://f.cloud.github.com/assets/39759/2223515/64ce3e0a-9a73-11e3-80a7-a69305301524.png)