Projectile

Changes in this release
- First change
- Second change

CmapTileHandler now allows `vmin` and `vmax` to be floats

- major breaking change to tile size API (see [c539472](https://github.com/sclabs/projectile/commit/c5394725c6a278354ca8e1c1250ad8d5248a21ad))

- added colormap support (see 1)

- custom HTML clients can now only be passed via the long flag `--client` since `-c` is now used by `-c/--cmap`

requests for tiles that don't actually fall on the image now return a
1x1 white pixel (hopefully allowing clients to fail quietly)

added support for images whose dimensions are not exact powers of two
- implemented by 1-padding tiles that fall on the edge of the image

added maximum tile size enforcement
- exposed as `-t/--tile_size` on the `projectile` command
- exposed as a `tile_size` kwarg throughout server setup
- stored on `TileHandler` as `TileHandler.tile_size`
- implemented via max pooling (per-channel if in RGB mode)
- added example to README showing how this effects performance

fixed an issue where the demo client would not be installed when installing via pip

initial release