Feature: Follow links: Allow hyphens and case-insensitive (PR #840 from @bratekarate)

Brief: Permits:

```
[Link to heading](#heading-example)
```

Issue: Feature Request: Support GFM anchor links inside wiki files #831
Original PR: Allow hyphens instead of spaces and search case-insensitive in jump_to_anchor function #840
Author: @bratekarate (implementation) @tinmarino (test)

Related: #666

test/link_markdown_multiple_per_file.vader

@@ -1,4 +1,40 @@
 # Link internal to a file
+# See issue #666 for anchor support (then internal links)
+
+
+# Link to anchor with spaces {{{!
+# PR #840
+# Issues: #831
+
+Given vimwiki (Internal links zith spaces):
+  [Any ! apparent name @#$](#basic-heading-many-spaces)
+  One line here
+
+  ## Basic HeAding Many SpacES
+
+  One line here
+
+Execute (Set markdown):
+  file wiki_test.md
+  call SetSyntax('markdown')
+
+Do (Enter link):
+  \<Cr>
+  A__HERE__\<Esc>
+
+Expect (Cursor at heading position):
+  [Any ! apparent name @#$](#basic-heading-many-spaces)
+  One line here
+
+  ## Basic HeAding Many SpacES__HERE__
+
+  One line here
+
+Execute (Clear wiki jumps (alias: prev_links)):
+  call vimwiki#vars#set_bufferlocal('prev_links', [])
+
+
+# Before {{{1
 
 Given vimwiki (Internal links + one link to filenew):
   # Contents
@@ -220,3 +256,5 @@ Expect (Some chars appended at self link):
   - [ this_is_18_chars My own file](wiki_test)
   - [Test1](#Test1)
   - [Test2](#Test2)
+
+# vim: foldmethod=marker foldlevel=30 sw=2