feat: migrate to ape and add features

[milkyklim]

closes #15

[banteg]

looks very solid! thank you.

things to think about:

• should we simplify funding to one transfer?
• should we use blueprint vs minimal proxy?
• should rug pullability be defined at creation? counterpoint: you can bundle multiple actions when deploying from a dao or safe.
• should we change admin change to a single step?
• it should be possible to recover the vested token sent to the contract minus still locked amount, add a test demonstrating that.

[banteg]

another decision:

• open_claim added to init with True by default to enable smart contract recipients like 0xsplits.xyz
• recipient can call set_open_claim(bool) which can set self.open_claim to False to disable this behavior
• set_open_claim is a noop if the value doesn't change
• emit SetOpenClaim(bool) if the value is changed
• the check in claim() is changed to assert msg.sender == recipient or (self.open_claim and recipient == beneficiary)

[banteg]

writing the full spec in #17, it supersedes all the comments

[banteg]

we should also log beneficiary

also let's use time instead of ts