purl-validator: Create PurlValidator for Python

[pombredanne]

Create PurlValidator written in Python.
Release this as a library and command line tool

[JonoYang]

The purl validator for python has been added in #26 . It is available at https://pypi.org/project/purl-validator/ . This contains a map of ~1.9 million purls that can be queried.

To test:

• Install purl-validator v0.0.1b1 release from pypi.org or this repo into a Python virtual environment
• In the environment, run a python shell and import the purl validator, instantiate it, and run some queries:

from purl_validator import PurlValidator
from package_url import PackageURL

pv = PurlValidator()

purl1 = PackageURL(type="cargo", name="quicksort", version="1")
purl2 = "pkg:bitbucket/connect2id/nimbus-content-type@2.3"

pv.validate_purl(purl1)
pv.validate_purl(purl2)