adding flags (singularity_options) to init command

[vsoch]

This will allow a user (using the Client) to add a list of any singularity options that are needed. E.g.,:

singularity --silent build ...

Could be passed to build like:

Client.build(..., singularity_options=["--silent"])

This will close #153

Signed-off-by: vsoch vsochat@stanford.edu

[vladdoster]

LGTM! Works like a charm! Thank you so so much for taking the time to do that!!

[vladdoster]

Here is --debug && --silent working!

[vsoch]

Great! I'll merge and release right away then. Thanks for the speedy testing!