Fallible rust stable std collections allocations

At the moment we have an unstabilized allocations API in the std, so this is a temporary safe solution for a stable rust.

Usage example

To create a vector you could use this code example: ``` use falliblealloc::vec::allocwith_size;

...

let vectorsize: usize = 10; let maybevector = allocwithsize::(vector_size);

match maybe_vector { Ok(vec) => println!("Created a vec with size 10"), Err(error) => println!("Failed to create a vec, reason: {}", error) } As you could see, the maybe_vector has aResult, AllocError> type```, so now it's possible to handle a part of allocation errors.

Also it's possible to change the allocator used by crate with this code example: ``` use std::alloc::{GlobalAlloc, System, Layout};

struct MyAllocator;

unsafe impl GlobalAlloc for MyAllocator { unsafe fn alloc(&self, layout: Layout) -> *mut u8 { System.alloc(layout) }

unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
    System.dealloc(ptr, layout)
}

}

[global_allocator]

static GLOBAL: MyAllocator = MyAllocator; ```