Most of the code in our the code base only puts a single space between
non-whitespace characters,

    "Like " + "this."

It is highly likely that there will not be a case where we will need to
put more than a single space between non-whitespace characters,

    "Like "  + "this."

To enforce consistency throughout the code base, let's add the
SingleSpaceSeparator module to our checkstyle configuration, and fix all
of the existing violations in our code base.