addresses issue #2753.
Formatting the JSON with the default parameters will escape the unicode
symbols in a way that c-lightning won't allow, leading to an exception.
Changelog-Fixed: `pylightning` now handles unicode characters in JSON-RPC requests and responses correctly.
This should not affect any consumer of the API since we just shift the actual
implementation from one side to the other, and keep aliases in place so
scripts don't break.
We also bump the version number from 0.0.7.3 to 0.7.4 which allows us to be in
sync with c-lightning itself, and remove the superfluous `0` in front.