Show modules in docs, fix doc warnings

src/coord.rs

 }
 
 /// A tile position in a tile pyramid.
-/// Each zoom level has 2^zoom by 2^zoom tiles.
-/// `x` and `y` are allowed to be negative or >= 2^zoom but then they will not correspond to a tile
+/// Each zoom level has 2<sup>zoom</sup> by 2<sup>zoom</sup> tiles.
+/// `x` and `y` are allowed to be negative or >= 2<sup>zoom</sup> but then they will not correspond to a tile
 /// and `is_on_planet` will return false.
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
 pub struct TileCoord {

src/main.rs

 extern crate xdg;
 
 #[macro_use]
-mod context;
-
-mod buffer;
-mod config;
-mod coord;
-mod map_view;
-mod map_view_gl;
-mod program;
-mod texture;
-mod tile;
-mod tile_cache;
-mod tile_atlas;
-mod tile_loader;
-mod tile_source;
+pub mod context;
+
+pub mod buffer;
+pub mod config;
+pub mod coord;
+pub mod map_view;
+pub mod map_view_gl;
+pub mod program;
+pub mod texture;
+pub mod tile;
+pub mod tile_cache;
+pub mod tile_atlas;
+pub mod tile_loader;
+pub mod tile_source;
 
 use clap::Arg;
 use coord::ScreenCoord;