Dark Mode (#912)

closes #704

app/components/Tab.js

@@ -8,21 +8,21 @@ const NavItem = styled(NavLink)`
   font-size: 11px;
   font-weight: 500;
   text-transform: uppercase;
-  color: ${props => props.theme.slate};
+  color: ${props => props.theme.textTertiary};
   letter-spacing: 0.04em;
   margin-right: 24px;
   padding-bottom: 8px;
 
   &:hover {
-    color: ${props => props.theme.slateDark};
+    color: ${props => props.theme.text};
   }
 `;
 
 function Tab(props: *) {
   const activeStyle = {
     paddingBottom: '5px',
-    borderBottom: `3px solid ${props.theme.slateLight}`,
-    color: props.theme.slate,
+    borderBottom: `3px solid ${props.theme.textTertiary}`,
+    color: props.theme.textTertiary,
   };
 
   return <NavItem {...props} activeStyle={activeStyle} />;