Add LevelDB caching to Blockchain.get_ordered_blocks(...)

[brannondorsey]

Addresses #39 + updates to README to reflect changes past and present.

[pep8speaks]

Hello @brannondorsey! Thanks for updating the PR.

• In the file blockchain_parser/blockchain.py, following are the PEP8 issues :

Line 207:80: E501 line too long (90 > 79 characters)

Comment last updated on March 15, 2018 at 19:42 Hours UTC

[coveralls]

Coverage remained the same at 94.053% when pulling 622949c on brangerbriz:master into 17d5119 on alecalve:master.

[brannondorsey]

@alecalve, would you like me to clean up some of these PEP warnings before merging?

[alecalve]

That'd be great!

[brannondorsey]

I've fixed all but one of the PEP formatting errors. Couldn't think of an elegant way to fix the last without changing code around too much so I figured ¯_(ツ)_/¯. Should be ready to merge.

[alecalve]

Thanks again!