Fix: VimwikiTOC is broken against headers with link (Issue #182)

Problem: VimwikiTOC and follow_link do not support header (anchor) with
link in their body

Solution:
- VimwikiTOC (easy): Create function base.vim s:clean_header_text that
converts [DESC](URL) -> DESC
- follow_link (hard):
-- [[URL]]: was already working due to punctuation removal.
-- [DESC](URL): Search for a potential `]([^)]*)` after every character

test/command_toc.vader

@@ -1,6 +1,8 @@
 # VimwikiTOC {{{1
 #
-# TODO implement: If link in the heading (see README.md)
+# Just generate the TOC
+# See: link_* for link movement and creation
+#
 # TODO (10min) test if g:vimwiki_to_header well readen
 # TODO (10min) test vimviki_toc_link_format
 # TODO (1h) test if really wiki dependant (for 2 diffrent wikis)
@@ -28,6 +30,30 @@
 #
 # Start {{{1
 
+Given vimwiki (With link header (#182) {{{1):
+  # A [link](anything here) B
+  # t[link](anything here)
+
+  ## 7.4.1528
+
+Execute (VimwikiTOC: Set syntax markdown && Set sw=8):
+  call SetSyntax('markdown')
+  set sw=8
+  VimwikiTOC
+
+Expect vimwiki (With link header (#182) {{{1):
+  # Contents
+
+  - [A link B](#a-link-b)
+  - [tlink](#tlink)
+          - [7.4.1528](#741528)
+
+  # A [link](anything here) B
+  # t[link](anything here)
+
+  ## 7.4.1528
+
+
 
 Given vimwiki (Underline header (SetExt) (#209) {{{1):
   First with spaces