Measurement and Enhanced Terrain Ruler fixes

• Update geometry lib to v0.1.5. Fix for incorrect diagonal measurement in grids (issue #3). Issue with dnd5e may still result in questionable rounded values when measuring Euclidean distances and 5/10/5 measurements on hex maps. See foundryvtt/dnd5e#2257 and foundryvtt/dnd5e#2256.
• Fix for updating ruler elevation label on gridless maps when increasing or decreasing elevation.
• Fix for measuring elevation for terrains created by Enhanced Terrain Elevation (issues #8, #15).