Add pip support

[uetchy]

So we can install coincheck-python with simply running pip install git+https://github.com/coincheckjp/coincheck-python.

Problem

coincheck in PyPI index is already taken from another user and that package is seemingly outdated.
We should contact them to obtain coincheck as official package?

Changes

• Add setup.py
• Add .gitignore
• Move test.py to /test
• All methods parse response json and return dict or array

[uetchy]

/ping @dogyearm @oxigen
What do you think?