v1.1.0-rc18

Adds whitespace cropping beta, smart chroma subsampling, and now uses stable Rust.

Now publishing builds and nuget packages for:

• Ubuntu 18.04 (64-bit)
• Ubuntu 18.04 (64-bit with haswell feature support)
• Ubuntu 16.04 (64-bit)
• OS X 10.11 (64-bit)
• Windows (32-bit)
• Windows (64-bit)
• WIndows (64-bit with haswell feature support)