Some early work on varous query objects.
Merge branch 'develop' into feature/query_parser
Work more on query tree structure.
More work on query tree structure.
More work.
Merge branch 'feature/parser' into feature/query_parser
More work on query parsing.
Literal parsing; term parsing hooks; unit test stubs.
More debug stuff.
Add center column, footer, transitions.

Add:
    static/sass/_mixins.sass
        -Add transition classes.

    static/sass/main.sass
        -Add base styling for footer, center column.

    templates/index.html
        -Add foundation `div` tree to `body`, and footer contents.
Finalize base template/styling; add _variables.

Add:
    static/sass/main.sass
        -Complete `template/layout.html` positioning rules.
        -Add some styling to the footer.

    static/sass/_variables.sass
        -Add `SASS` partial to contain all project-wide variables.

    templates/index.html
        -Add project-wide layout template (should've been packaged into the
        previous commit).
Add flooring to footer.

Add:
    templates/layout.html
        -Add `header`, `body`, and `footer` divs, for greater modularity and to
        floor the footer.

    static/sass/main.sass
        -Add styling to the new footer, which is always floored to the bottom of
        the page (even when an otherwise insufficient amount of content is
        present).
Parsing dates should work.
Fix a typo.
Symbol parsing works.
Finish parsing for languages.
More complete and descriptive error messages.
Construct full trees; support inverting with not:<term>.
Change UnaryOp.NOT to work with BinaryOp.{OR,AND}
code