Add support for startup scripts

[jamdagni86]

Jupyter (IPython) supports startup scripts. When the kernel starts, it loads all the files present in the startup directory (usually ~/.ipython/profile_default/startup or ~/.jupyter/startup) in lexicographical order.

Add support for loading any *.go files found in the directory during startup.

[jamdagni86]

@yunabe - I'm thinking we can change jupyter/gojupyterscaffold/gojupyterscaffold.go:NewServer function to load startup scripts before returning. I'm more inclined towards loading the scripts from ~/.jupyter/startup as Jupyter doesn't support IPython profiles. Let me know your thoughts!

[yunabe]

Sorry for the slow response. I think it's a good idea to support startup scripts. But before desining and implementing actual code, I would like to make clear what we really want to do with startup scripts.

jamdagni86, what do you really want to do with start-up scripts?
Do you want to import some common packages like "fmt"? Do you want to execute some initliazation code everytime we start the kernel?

I do not want to make the start-up time longer unnecessarily by supporting start-up scripts. So, I would like to make clear what we really want to achive with start-up scripts.

Thanks,
yunabe

[jamdagni86]

@yunabe - the idea is to have common functions/imports which people usually import once they start up the lgo kernel (say a function to connect to a db or as you said, common packages like "fmt"). As you rightly said, giving this option to the user could potentially slow up starting the kernel. But I guess, it's upto the user to take that decision to add code which slows the startup down.