Factor out styles

src/components/index.js

@@ -6,15 +6,22 @@ const React = require('react');
 const { Link } = require('react-router-dom');
 const { Tooltip } = require('@material-ui/core')
 
+const popupStyle = {
+    fontSize: '14px',
+};
+const textStyle = {
+    fontWeight: 'bold',
+};
+
 function get_pathname(reference) {
   return { pathname: TERMS_DIR + reference };
 }
 
 const Term = ({children, reference, popup}) => {
   return (
-    <Tooltip title={<span style={{fontSize: '14px'}}>{popup}</span>} arrow={true}>
+    <Tooltip title={<span style={popupStyle}>{popup}</span>} arrow={true}>
       <Link to={ get_pathname(reference) }>
-      	<span style={{fontWeight: 'bold'}} >{children}</span>
+      	<span style={textStyle}>{children}</span>
       </Link>
     </Tooltip>
   );