Set up Travis-CI to auto-deploy site

[angela-li]

Here's how to do it:

1. Enable the use of Travis-CI on this repository (may need to do through your Travis-CI account), aka give permission for the Travis bots to operate on this repository. Angela can set up this if needed. You can also create a Travis-CI account.
2. Include a .travis.yml file in the development branch that basically is a copy of this .travis.yml file from the ChiRCollab website, except modify lines 26-28 to be:

 branch: development
    local_dir:          # or even just get rid of this line
    repo: rladies-chicago/rladies-chicago.github.io

Here's documentation from the official blogdown site:

• Blogdown documentation reference, if you want to read more!