[GEARPUMP-305][Doc] Use MkDocs plugin to validate html

Get rid of ruby tools

Author: manuzhang <owenzhang1990@gmail.com>

Closes #252 from manuzhang/html_proofer.
diff --git a/docs/README.md b/docs/README.md
index d193c86..8e87ae2 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -5,39 +5,10 @@
 
 # Requirements
 
-You need to install ruby and ruby-dev first. On Ubuntu, you ca run command like this:
+We use [MkDocs](https://www.mkdocs.org/) (>=0.17) to generate our documentation site. You can install
+it via:
 
-    sudo apt-get install ruby
-    sudo apt-get install ruby-dev
-    sudo apt-get install python-setuptools
-    sudo apt-get install pip
-
-We use Markdown to write and Jekyll to translate the documentation to static HTML. You can install
-all needed software via:
-
-    sudo pip install mkdocs
-    sudo gem install html-proofer
-
-
-If you are using Mac OSX 10.11+ (El Capitan), you will need to execute following command:
-```
-sudo gvim /Library/Ruby/Gems/2.0.0/gems/ffi-1.9.10/lib/ffi/library.rb
-```
-And change following code in this file:
-```ruby
-module FFI
-...
-    def self.map_library_name(lib)
-        ...
-        lib = Library::LIBC if lib == 'c'
-        lib = Library::LIBCURL if lib == 'libcurl'
-...
-module Library
-    CURRENT_PROCESS = FFI::CURRENT_PROCESS
-    LIBC = '/usr/lib/libc.dylib'
-    LIBCURL = '/usr/lib/libcurl.dylib'
-```
-
+    pip install mkdocs
 
 # How to Build
 Command `./build_doc.sh` can be used to create a full document folder under site/. 
@@ -67,5 +38,5 @@
 
 Command `mkdocs build` can be used to make a test build.
 
-Command `mkdocs serve` can be used for debug purpose. Mkdocs will start a web server at
+Command `mkdocs serve` can be used for debug purpose. MkDocs will start a web server at
 `localhost:8000`. Use this mode to experiment commits and check changes locally.
diff --git a/docs/build_doc.sh b/docs/build_doc.sh
index 5acd4ed..19e3325 100755
--- a/docs/build_doc.sh
+++ b/docs/build_doc.sh
@@ -50,13 +50,6 @@
 # generate site documents
 mkdocs build --clean
 
-# check html link validity
-echo "Checking generated HTMLs using htmlproofer..."
-
-htmlproofer site \
-  --disable-external \
-  --file-ignore site/base.html,site/breadcrumbs.html,site/versions.html,site/toc.html,site/footer.html
-
 # generate API doc
 if [ "$BUILD_API" = 1 ]; then
   # Build Scaladoc for Java/Scala
diff --git a/docs/mkdocs.yml b/docs/mkdocs.yml
index 1a11429..13735aa 100644
--- a/docs/mkdocs.yml
+++ b/docs/mkdocs.yml
@@ -54,6 +54,7 @@
 plugins:
     - search
     - markdownextradata
+    - htmlproofer  
         
 extra:
     GEARPUMP_VERSION: "0.8.5-SNAPSHOT"