v0.18.0

Changes

• ECMap / ECRadar: Add interpolation init parameter to smooth the WMS-rendered radar layer instead of leaving it pixelated, using the INTERPOLATION=TRUE WMS parameter (suggested in #143). Defaults to False, matching previous behaviour
• ECMap / ECRadar: Add webp init parameter to request the radar layer from Environment Canada's WMS as WebP instead of PNG, and return get_latest_frame()/get_loop() output as WebP instead of PNG/GIF, trading lower bandwidth for higher per-frame latency. Defaults to False, matching previous behaviour