fix active_shims()

[beanumber]

This currently doesn't work:

fertile/R/utils.R

Line 736 in 639fc68

# doesn't work -- need to fix

When we shim functions, we should add a "package" attribute to the function. Then, any function that is in any environment that has a "package" attribute equal to "fertile" can be safely removed. We can use this functionality in active_shims() and by extension, in unload_shims().

[ambertin]

Got this partially addressed in #104 but still having an issue with some shims. I will try to look into that soon, but for now at least the function is at least mostly functional. Certainly better than it was before.