Use Sass preprocessor for CSS styling.

- Include Sass, Bourbon, and sprockets-sass as dependencies in Bundler.
- Restructure the stylesheets folder.
- Rename the application.css to scss extension with Sass support.
- Start moving common values into the variables scss file.
- Ignore the .sass-cache folder from git tracking.
Minor updates of styling to index view.

For the left and right div elements, they need to be in their own
container, otherwise Gridism won't apply padding correctly and the
left div will not be aligned correctly. Also, the font styling was
modified slightly to add some spacing in between the letters of the
names, date, and location text.

- Fix issues with content area that is not using Gridism correctly.
- Add letter-spacing to the text in the content area.
Add slight shadow to cover image.

- Set the image container with class element of cover.
- Set a box-shadow on the image selector within cover class.
Update index view with style changes and text additions.

- Include new section, announcement, for some more information.
- Set background-color to white for body and remove padding.
- Add background-color to card section and add padding from body.
- Write out announcement text about upcoming things to expect.
Modify layout of details div under card section.

- Remove spacing between city, state, names, and date.
- Reduce the letter-spacing for the state text.
- Wrap the details div in a grid (Gridism).
Exclude tracking of webfonts directory from git.