Replace three.min.js in introduction docs

Replace three.min.js with non-minified version in the "create your first scene" introduction. 
Continuing from there beginners will have a hard time debugging their code using the minified version.

Add getShaderPrecisionFormat polyfill

New RingBufferGeometry

RingGeometry `s BufferGeometry port

Expanding documentation for api/object/LineSegments

Blender exporter: optionally export Custom Properties as userData.

Minor additions to new BufferGeometry

Fix for when maxInstancedCount is 0 at WebGLRenderer

Fix for geometry text pnltri and earcut examples

Updated VRControls and VREffect to support WebVR v1

Based on suggestions by @cvan and @jzitelli

Fix for geometry.maxInstancedCount == 0

Fix for geometry text pnltri example

Fix for geometry text earcut example

Materials: Setting THREE.PremultipliedAlphaBlending as default blending for relevant built-in materials. See #8255.

Fix proposal for issue #8244

New CylinderBufferGeometry