Change Promise.thenPipe to use template types instead of std::function

[murillo128]

When compiling with Visual Studio 2015 I am getting the following compilation errors:

> src\FireWyrm\AlienWyrmling.cpp(125): error C2664: 'FB::Promise<FB::variant> FB::Promise<void>::thenPipe<FB::variant>(std::function<FB::variantPromise (void)>,std::function<FB::Promise<FB::variant> (std::exception_ptr)>) const': cannot convert argument 1 from 'FB::FireWyrm::AlienWyrmling::Invoke::<lambda_7d0129f19c4193e2d5fbf9013690dec1>' to 'std::function<FB::variantPromise (void)>'
>  src\FireWyrm\AlienWyrmling.cpp(125): note: No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called

It seems that msvc-14 is not able to cast lambda functions to std::functions that is what the thenPipe method expects.

This is a tentative (unproven and not tested on other c++ compilers) to try to address it.

The PR has two main changes:

• Change the method parameters to template types that are automatically inferred by the compiler
• Due to previous change, when calling with only 1 argument, the type of the second parameter cannot be inferred, and if set to null if fails as null don't have the expected methods. So I have duplicated the thenPipe methods in two one for success only callback and another with the success and fail callback

I am mostly sure that this PR is not ready for merging, but I hope it is worthy as a starting point.