Update version of Jekyll in README (envygeeks#218)

README.md

@@ -17,7 +17,7 @@ The standard images (`jekyll/jekyll`) include a default set of "dev" packages, a
 #### Usage
 
 ```sh
-export JEKYLL_VERSION=3.5
+export JEKYLL_VERSION=3.8
 docker run --rm \
   --volume="$PWD:/srv/jekyll" \
   -it jekyll/jekyll:$JEKYLL_VERSION \
@@ -31,7 +31,7 @@ The builder image comes with extra stuff that is not included in the standard im
 #### Usage
 
 ```sh
-export JEKYLL_VERSION=3.5
+export JEKYLL_VERSION=3.8
 docker run --rm \
   --volume="$PWD:/srv/jekyll" \
   -it jekyll/builder:$JEKYLL_VERSION \
@@ -47,7 +47,7 @@ The minimal image skips all the extra gems, all the extra dev dependencies and l
 ***You will need to provide a `.apk` file if you intend to use anything like Nokogiri or otherwise, we do not install any development headers or dependencies so C based gems will fail to install.***
 
 ```sh
-export JEKYLL_VERSION=3.5
+export JEKYLL_VERSION=3.8
 docker run --rm \
   --volume="$PWD:/srv/jekyll" \
   -it jekyll/minimal:$JEKYLL_VERSION \
@@ -56,14 +56,14 @@ docker run --rm \
 
 ## Dependencies
 
-Jekyll Docker will attempt to install any dependencies that you list inside of your `Gemfile`, matching the versions you have in your `Gemfile.lock`, including Jekyll if you have a version that does not match the version of the image you are using (you should be doing `gem "jekyll", "~> 3.6"` so that minor versions are installed if you use say image tag "3.5".
+Jekyll Docker will attempt to install any dependencies that you list inside of your `Gemfile`, matching the versions you have in your `Gemfile.lock`, including Jekyll if you have a version that does not match the version of the image you are using (you should be doing `gem "jekyll", "~> 3.8"` so that minor versions are installed if you use say image tag "3.7.3").
 
 ### Updating
 
 If you provide a `Gemfile` and would like to update your `Gemfile.lock` you can run
 
 ```sh
-export JEKYLL_VERSION=3.5
+export JEKYLL_VERSION=3.8
 docker run --rm \
   --volume="$PWD:/srv/jekyll" \
   -it jekyll/jekyll:$JEKYLL_VERSION \
@@ -81,7 +81,7 @@ You can enable caching in Jekyll Docker by using a `docker --volume` that points
 ### Usage
 
 ```sh
-export JEKYLL_VERSION=3.5
+export JEKYLL_VERSION=3.8
 docker run --rm \
   --volume="$PWD:/srv/jekyll" \
   --volume="$PWD/vendor/bundle:/usr/local/bundle" \
@@ -159,7 +159,7 @@ This image supports [jekyll-reload](https://rubygems.org/gems/jekyll-reload), al
 #### Usage
 
 ```sh
-export JEKYLL_VERSION=3.5
+export JEKYLL_VERSION=3.8
 docker run --rm \
   --volume=$PWD:/srv/jekyll \
   -p 35729:35729 -p 4000:4000 \