define new component with np requires config.py

[sean-lockwood]

If the user does not have a ~/.glue/config.py file containing an import for numpy, then they are unable to define new components containing np in the expressions.

[sean-lockwood]

In core/parse.py, the global environmental variables don't necessarily include np. Perhaps import it and add it to the env dict there?

[astrofrog]

@sean-lockwood - good idea - I'm working on this here: #956 (I'm going to make some more improvements before merging it)

[astrofrog]

@sean-lockwood - I've now merged in some changes that make it possible to use numpy, np, and math. You can either try the latest developer version of glue, or I will release 0.8 soon which will include these changes. Let me know if you run into any issues!