Fix default password for rocker/rstudio

[nielsaka]

Description

The default password rstudio seems to be broken. Instead, use server. Combining user name rstudio and password server reads nicely as rstudio server.

The default password was changed for debian_install_rstudio() , docklet_rstudio(), and docklet_packrat()

All tests passed. I updated the docs, but I am not sure if that is desired.

(also, fixed a small typo in the docs)

Related Issue

fix #170

[sckott]

A way we could FORCE users to create their own password would be to not have a default value for password, so if they don't give a value to it, then the function call fails. e.g.,

docklet_rstudio <- function(droplet, password, user = 'rstudio', ...)

If we do that, password should be moved to before user, as we don't want to have a required/no default value parameter after one that has a default value

thoughts?

[nielsaka]

Sounds good to me. Another option would be to leave both user and password without default values. It would make sense to me that any user would have to specify at least these two parameters.

I would be happy to implement either.

[sckott]

@nielsaka sounds good to have both user and password be required (without default values)