updated to jekyll 3.9.2 partially resolving issue (#313)

[nick-mon1]

WIP, currently blocked at jekyll 3.9.2.

Resolves issue #313

• Update to Jekyll 4.2.2
• Use ruby >= 2.4.0
• Update bundler
• Update bundler dependencies

Jekyll is blocked with the following gem dependencies:

Bundler could not find compatible versions for gem "jekyll":
In Gemfile:
jekyll (~> 4.2.2)

jekyll_pages_api_search was resolved to 0.5.0, which depends on
  jekyll_pages_api (~> 0.1.4) was resolved to 0.1.6, which depends on
    jekyll (>= 2.0, < 4.0)

May need to consider replacing jekyll_pages_api with another gem.

• Consider Jekyll 4.x support 18F/jekyll_pages_api#47
• https://github.com/18F/jekyll_pages_api_search

[nick-mon1]

We can update to jekyll 4.2.2 but will have to drop the current jekyll_pages_api_search gem because it does not support jekyll 4

Implementing search.gov search service will require some additional effort, this would be a multi-step process and some coordination with the search.gov team to integrate with the site. Additional testing will be required to make sure the search results page looks good and performs as expected.

In the meantime we can update to jekyll 3.9.2 and still use the current search features until we decide to complete the search.gov integration.

• Video Instructions: Introduction to Search.gov
• https://search.gov/get-started/

[mejiaj]

Looks good so far, just a few things. A question about commented line regarding jekyll version.

Could we also look into updating .bundler-version? The last update was 3 years ago.

[nick-mon1]

I've updated to bundler 2.3.15, the most current version.