[Problem] Testnet node hosting guilde is not updated

[lezzokafka]

The docs needs to be updated accordingly with the testnet upgrade from v0.6.* to v0.7.*

1. run 0.6.0-testnet until block 1553700
2. upgrade to 0.7.0-rc1-testnet and update ~/.cronos/config/app.toml (link) and resume to sync from block 1553700

[aw126]

Updated at #110