@xrange/core

The very core of xrange, provided as a separate package

Differences from xrange:

• only numeric implementation with two or three numeric arguments: xrange(start, stop, step?);
• no proper support of decimal numbers, only integers;
• no custom errors, such as "argument is required" or "argument must infinite";
• no intelligent boundary swapping, — e.g., xrange(10, 1) will not iterate;
• only Node.JS is supported (for now at least);