Fix Renaming and HTML Exporting Issue (#1057)

On Windows.

Commits squashed from first to be committed to most recent:
* fix subdir not correct when path using `\`

* fix slice by variable value not supported in vim 7.3

* remove last '\' from path in CustomWiki2HTML

* fix CSS path in CustomWiki2HTML wrong

* remove unused confirm CustomWiki2HTML

* use ==# rather than == in shellescape html.vim

* remove "FIXME this can terminate in the middle of a path component! from
base#subdir

* update doc/vimwiki.txt

* update contributor to doc/vimwiki.txt

* add comment in html#shellescape

doc/vimwiki.txt

@@ -3892,6 +3892,7 @@ Contributors and their Github usernames in roughly chronological order:
     - Amit Beka (@amitbeka)
     - Yuuy Wei
     - Yifan Hu (@yhu266)
+    - Levi Rizki Saputra (@levirs565)
 
 ==============================================================================
 16. Changelog                                              *vimwiki-changelog*
@@ -3946,6 +3947,8 @@ New:~
 Changed:~
     * PR #1047: Allow to replace default mapping of VimwikiToggleListItem
     * VimwikiCheckLinks work on current wiki or on range
+    * PR #1057: Change how resolve subdir work
+      Change how shell escaping work when using CustomWiki2HTML
 
 Removed:~
 
@@ -3977,6 +3980,8 @@ Fixed:~
     * PR #959: Fix :VimwikiNextTask
     * PR #986: Fix typo in help file
     * PR #1030: Allow overwriting insert mode mappings
+    * PR #1057: Fix renaming, updating link, and exporting HTML subdir wrong
+      Fix resolve subdir return wrong path in Windows
 
 
 2.5 (2020-05-26)~