Revert "Document restored ability to set config using ENV vars."

This reverts commit 80974dbcf0ef570ded99c3ff07d597246701de39.
Revert "Restore ability to set config from ENV vars."

My apologies, world; all this time this song is best. The aim of
allowing Redimap config to be set directly via ENV vars was to make it
easier to work as a service as part of a larger application (such as in
a Procfile). However, usage indicated that many things expect ENV vars
to be uppercased, so the ENV vars didn't turn out to be as useful as
hoped. In addition, it really is rather easy to set ENV vars, if you
so desire, using the command-line parameters, such as `-h $IMAP_HOST`.
Supporting ENV vars directly adds bloat to the code.

So, no direct ENV var support for Redimap. If including as a library,
use a configure block. If running as a service, specify command-line
parameters. If you'd like to use ENV vars, simply pass those as
command-line parameters.

This reverts commit 16daf880c83dcb63d42b395a4e7513f3d159cdbc.
Merge branch 'remove-env-vars' into develop
Fix example command-line parameters in README.
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
Refactor lib/redimap/base into lib/redimap.
Simplify logger calls in ImapConn,RedisConn.
Test ImapConn.
Replace test subject syntax with explicit object.

Simply because I find it easier to read. ;) And also because it's more
flexible with those tests requiring extra setup before the 'do' part is
called.
Refactor ImapConn test, creating imap_conn_new.
Test RedisConn, making fixes.

Fix 'rescue' vs 'resque' typo throughout.
Merge branch 'tests' into develop
Bump version to v0.6.0.
Merge branch 'release/v0.6.0'