Fetches category (or categories) of content hosted by a domain according to DMOZ.
The function checks if path to the DMOZ file is provided by the user.
If not, it looks for
dmoz_domain_cateory.csv in the working directory. It also returns
results for prominent subdomains.
vector of domain names
path to the dmoz file, which can be downloaded using
data.frame with original list and content category of the domain
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