Separate active tags by instead of &

Using `&` to separate tags in path (like
`/tags/currently&selected&tags`) may interfer with tags including `&`
character (like `black&white`). Since ` ` is replaced with `_` when
adding tag to notes, it's ideal separator because it's guaranteed that
tags are not including this character.

browser/main/NoteList/index.js

@@ -343,7 +343,7 @@ class NoteList extends React.Component {
     }
 
     if (location.pathname.match(/\/tags/)) {
-      const listOfTags = params.tagname.split('&')
+      const listOfTags = params.tagname.split(' ')
       return data.noteMap.map(note => {
         return note
       }).filter(note => {

browser/main/SideNav/index.js

@@ -196,7 +196,7 @@ class SideNav extends React.Component {
     if (tags === 'alltags') {
       return []
     }
-    return tags.split('&')
+    return tags.split(' ')
   }
 
   handleClickTagListItem (name) {
@@ -229,7 +229,7 @@ class SideNav extends React.Component {
     } else {
       listOfTags.push(name)
     }
-    router.push(`/tags/${listOfTags.join('&')}`)
+    router.push(`/tags/${listOfTags.join(' ')}`)
   }
 
   emptyTrash (entries) {