Suggestion: E-Steps calibration

[mfraser]

I recently calibrated my E-steps and might've found an easier way of doing it.

1. Heat up the hot-end to allow the extruder to function.
2. Remove any filament that is inside the Bowden tube.
3. Remove the Bowden tube from the extruder.
4. Push filament through the extruder until it comes out of the coupling.
5. Snip the end of the filament so that it is flush.
6. Extrude 100mm of filament.
7. Measure the extruded length of filament with a digital caliper.
8. Do the calculations and set the E-Steps.
9. Remove the filament and go back to step 4 to check.

This means no wasted filament and not having to mark the filament with a pen which can be difficult to measure.