v1.4.0: Generic support

This updates the Go version and adds support for generics, replacing the type Sample interface{}.

Version 1.3.0: Pre-allocate main buffers

Merge pull request #14 from lightstep/jmacd/pre_alloc

Pre-allocate main buffers

Version 1.2.0: Memory re-use support

This adds a Reset() method to support re-using Varopt samplers.
This adds an "ejected value" return from Add() to support re-using Sample items.

Version 1.1.0: Optimizations

Adds an error return value to Add(), indicating weights <= 0 or NaN.
Optimizes the sample heap by inlining the heap to avoid interface conversions.

Version 1.0.0: Initial release

This is the first release of lightstep/varopt.