Rename .refine into .refineUnsafe

[matwojcik]

Is your feature request related to a problem? Please describe.
.refine method does not indicate that it is unsafe - i.e. can throw exception. It is so easy to make a mistake by a developer when they don't know the library very well. I think one of the goals of libraries like this is to promote type safety and purity.

Describe the solution you'd like
I suggest in 3.x to rename it to refineUnsafe

[Iltotore]

Adding refineUnsafe to the next minor and marking refine as deprecated is also an option. Then, we can more safely remove refineUnsafe for 3.0.0.

[matwojcik]

Adding refineUnsafe to the next minor and marking refine as deprecated is also an option. Then, we can more safely remove refineUnsafe for 3.0.0.

Definitely good idea. Prepared PR #204 that addresses this