The previous API was inconsistent. The new one is
```js
--parser flow
--parser babylon
{parser: 'flow'}
{parser: 'babylon'}
```
if we ever want to add new parsers in the future it'll allow that more easily.
I put a console.log in parser.js in both functions and tested that the test suite worked both with and without the change in run_spec. I also tested that both the previous and new command line options are working.
At some point in the future we'll likely want to get rid of the old api but might as well keep supporting it so we don't break anyone for now.
When looking into adding a test, I realized that the logic was inside of bin/prettier.js and therefore only applying to the cli. Moving it to index.js and adding a test so that it's more robust :)
* treat shebang outside of parsing
* use less costly indexOf and reuse format function
* avoid reprinting new line and potential double space at start
* move options back to format function
Although prettier lacks options to filter project files to format by itself, most shells allow to submit multiple files with a filename expansion. Add an example using bash.
Christopher Chedeau