Issue with typecasting in assertions

[djrtwo]

Issue

Vyper performs implicit conversion for ==, causing a few previously uncaught sources of error.

For example in deposit and logout function, assert self.current_epoch == block.number / self.epoch_length which converts self.current_epoch to decimal rather than converting block.number / self.epoch_length to an int. This line should instead be assert self.current_epoch == floor(block.number / self.epoch_length).

Proposed implementation

• Fix assertions mentioned above
• Comb the contract for other incorrect implicit type casting and fix
• add any relevant tests.

[djrtwo]

Addressed in #56