Generate CSS assets during build

The main CSS file will import everything from Bootstrap and
Font Awesome and provide a way to override things.

ui/build.rs

@@ -0,0 +1,20 @@
+// Generates static assets.
+
+use std::env;
+use std::fs::File;
+use std::io::Write;
+use std::path::Path;
+
+use sass_rs::{self, Options};
+
+fn main() {
+    let dir = env::var("CARGO_MANIFEST_DIR").unwrap();
+    let scss_dir = Path::new(&dir).join("scss");
+    let source_css_file = scss_dir.join("stoptime.scss");
+    let css_dir = Path::new(&dir).join("static").join("css");
+    let target_css_file = css_dir.join("stoptime.css");
+
+    let sass = sass_rs::compile_file(&source_css_file, Options::default()).unwrap();
+    let mut f = File::create(&target_css_file).unwrap();
+    f.write_all(sass.as_bytes()).unwrap();
+}

ui/scss/stoptime.scss

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+// Include all of Bootstrap.
+@import "bootstrap/bootstrap";
+
+// Include all of Font Awesome.
+@import "fontawesome/fontawesome";
+
+/* StopTime's main CSS (overrides)
+ */
+
+// Prepare for the fixed-top navbar.
+html {
+  position: relative;
+  min-height: 100%;
+}
+
+// Add some padding for the fixed-top navbar.
+body {
+  padding-top: 80px;
+  margin-bottom: 24px;
+}
+
+footer {
+  position: absolute;
+  bottom: 0;
+  width: 100%;
+  height: 24px;
+  line-height: 24px;
+}