validate lambda parameters for uniqueness and add more tests

[ix0rai]

adds lambdas into the mix for parameter uniqueness validation.

known issues:

• names are not checked into lambdas (renaming a parameter of a top level method into a conflict with a parameter of an enclosed method will not throw an error)

fixes #188

[ix0rai]

names are not checked into lambdas (renaming a parameter of a top level method into a conflict with a parameter of an enclosed method will not throw an error)
should we even do this?

[IotaBread]

Looks great!