Cleanups

[stas]

• linter cleanups
• refactored the safe calls due to revert_on_failure cancelling the success return value
• unified tests to use CHAIN_ID env var

---

Gas estimates

v0.3.10

>>> lpold1 = LpSugar.at("0x51f290CCCD6a54Af00b38edDd59212dE068B8A4b")
>>> lpold1.forSwaps.estimate_gas(2000, 0, {'from': account})
42445612
>>> lpold1.all.estimate_gas(500, 0, {'from': account})
33651074
>>> lpold1.positions.estimate_gas(200, 0, account.address, {'from': account})
8531733
>>>

v0.4

>>> lp1 = LpSugar.at('0xd0bF8A2e7ECAC81106b3A1A341299E9314219598')
>>> lp1.forSwaps.estimate_gas(2000, 0, {'from': account})
22197632
>>> lp1.all.estimate_gas(500, 0, {'from': account})
34532068
>>> lp1.positions.estimate_gas(200, 0, account.address, {'from': account})
10043633

[pedrovalido]

lgtm,
really like these changes 🚀

(needs the ci fixed before merging)