v1.2.2

• [Fix] differentiate -0 from 0 (#8)
• [Robustness] cache Object.prototype.toString
• [Performance] avoid recreating lowbyte function every time
• [Performance] check for primitive types as early as possible.
• [Robustness] use typeof instead of comparing to literal undefined
• [Refactor] explicitly coerce Error objects to strings
• [Refactor] remove unneeded elses
• [Refactor] consolidate wrapping logic for boxed primitives into a function
• [Refactor] consolidate Map/Set notations.
• [Refactor] split up var declarations for debuggability
• [Refactor] move object key gathering into separate function
• [Tests] up to node v7.7, v6.10, v5.12, v4.8; improve test matrix
• [Tests] ensure that this function remains anonymous, despite ES6 name inference.
• [Dev Deps] update tape