Move no_nitime, no_nilearn checks

[berleant]

see #1647 (comment)

[mgxd]

@shoshber is this all set? if so, can we close?

[berleant]

It isn't done. I've copied the original request here for clarity:

@satra said: "the check [no_nilearn, no_nitime]m]should be used inside run interface to indicate to the user that they need to install nilearn. at this point if they use this interface, it will result in an error deep in the code."

But of course, feel free to close the issue again if this is a minor enough issue.