Allow both 0.7.0 and 0.7.0a1 for ipfshttpclient

[brunneis]

What was wrong?

The ipfshttpclient version was fixed to 0.7.0a1. However, 0.7.0 was released already with "No changes compared to 0.7.0a1" (https://github.com/ipfs-shipyard/py-ipfs-http-client/blob/master/CHANGELOG.md).

py-ipfs-http-client 0.7.0 (15.03.2021)

• No changes compared to 0.7.0a1 – breaking changes delayed to the unknown future

Since the version is fixed, web3.py cannot be installed when ipfshttpclient==0.7.0 is installed.

How was it fixed?

Under setup.py, install_requires was updated so both versions are supported.

[kclowes]

Thanks for the contribution @brunneis! Since there aren't any changes between 0.7.0a1 and 0.7.0, let's just specify 0.7.0. I'll update and merge!