Add a minimum version requirement on taxadb and wait to release the next version of this package

[amoeba]

Stemming from #333, @jeanetteclark found that we need to wait to release the next version of this package until taxadb 0.1.4 is on CRAN and that we should set a minimum version on taxadb for this package.

[cboettig]

longterm we should move to taxalight which is faster as a names resolver.

Also, the lack of resolution in both contentid and taxadb is currently due to hash-archive.org backlog causing it not to process new entries. The new releases of those packages merely add more default registries, which allow the hashes to be resolved.