Ran `rspec --init`.
Add skeletal Mapper#query and SQLResult#rows.

No actual database yet.
Move SQLResult to SQL::Result.
Add local .irbrc file.

Requires ~/.irbrc to have code to load local .irbrc file.

Adds `reload!` to reload the gem, as recommended by http://stackoverflow.com/a/23677820.
Add rubygems-tasks, to get `rake console`.

Easiest way to follow the [Ernie Miller Rule] for gems -- this way
is only 3 lines instead of 7.

[Ernie Miller Rule]: http://erniemiller.org/2014/02/05/7-lines-every-gems-rakefile-should-have/