function start() {
		if ( hasTicked ) {
			self.fail( '.tic() called more than once' );
		} else {
			self.emit( 'tic' );
			hasTicked = true;
			time = tic();
		}
	}
Starts a benchmark timer.

## Notes

-   Using a scoped variable prevents nefarious mutation by bad actors hoping to manipulate benchmark results.
-   The one attack vector which remains is manipulation of the `require` cache for `tic` and `toc`.
-   One way to combat cache manipulation is by comparing the checksum of `Function#toString()` against known values.

@private