Remove all RSpec tests.

The coverage was very patchy, and not very useful. Remove RSpec along
with all tests, to provide a clean slate for testing.

Indeed.
Test Redimap::VERSION.

Tests use Minitest. To run all tests:

    ruby -rminitest/pride test/redimap.rb
Test Config, making fixes.

Remove spurious require, and force #to_s to call #to_s on hash.
Document running of tests in README.

Includes pun. Har har.
Fix string description of Redimap::VERSION test.
Merge branch 'tests' into develop