Prevent ensembldb from attaching and masking dplyr

[mjsteinbaugh]

When using ensembldb to access AnnotationHub, the package attaches and masks dplyr::filter(). Here's a minimal example:

library(basejump)
filter
# namespace:stats
library(tidyverse)
filter
# namespace:dplyr
anno <- annotable("Homo sapiens")
filter
# namespace:ensembldb

We need to add a detection step to check if ensembldb is attaching, and make sure it is unattached after an annotable() call.

[mjsteinbaugh]

Fix is documented in latest commit on develop branch.