Exposed removeAllStubs from Swift API

[AllDmeat]

Checklist

• [x] I've checked that all new and existing tests pass
• [x] I've updated the documentation if necessary
• [ ] I've added an entry in the CHANGELOG to credit myself

Description

In my tests I'm importing OHTTPStubsSwift for stubbing, but I need to import OHTTPStubs as well just for stubs removal. I've added removeAllStubs() method right beside other Swift Syntax Sugar helpers to omit this requirement.

[AllDmeat]

@AliSoftware