Node2Vec sklearn-like interface

[dokato]

• Does this PR have a descriptive title that could go in our release notes?
• Does this PR add any new dependencies?
• Does this PR modify any existing APIs?
  • Is the change to the API backwards compatible?
• Have you built the documentation (reference and/or tutorial) and verified the generated documentation is appropriate?

Reference Issues/PRs

Implements enhancement mentioned in #566.

What does this implement/fix? Briefly explain your changes.

Node2Vec sklearn-like interface to be consistent with other embedding methods that support this syntax.

Any other comments?

PTAL @daxpryce . I wasn't sure about backward compatibility here, in particular is someone still wants to use a function, they need to change:

from graspologic.embed import node2vec_embed as node2vec

to

from graspologic.pipeline.embed import node2vec_embed as node2vec

[ghost]

All CLA requirements met.

[daxpryce]

@Nyecarr can you take a look at this and review?