Signed-off-by: Rémy Coutable <remy@rymai.me>

Fix: Correctly set logger options from Guardfile

Fix style violations for PR #892.

The Guard::Dsl#logger method was accidentally ignoring the user provided
options. This fixes that, so that the instructions provided in the Guard
wiki (see https://github.com/guard/guard/wiki/
Guardfile-DSL---Configuring-Guard#logger) are accurate again.

Test two scenarios:
- User can customize logger template
- User can customize logger level

CONTRIBUTING.md: add links to the wiki

There is some good documentation in the wiki which helps (plugin)
developers, so make it a bit easier to find.

Improved headings

Improved the headings in the README. Changed all headings to the same syntax, fixed heading levels and changed to bold where headings were used for emphasis.

CI against Ruby 2.2.8/2.3.5/2.4.2

Fix lumberjack version runtime dependency to `">= 1.0.12", "< 2.0"`

Run core with same Ruby version as it was started with.

https://github.com/guard/guard/issues/863

Travis: update CI matrix to include latest release of JRuby

  - this allows JRuby code coverage data to be created

README: Build badge shows master branch status

  - [ci skip]

Add aliasing section inside tired-of-typing bundle exec 

Signed-off-by: Rémy Coutable <remy@rymai.me>

`guard -c` nows clears window buffer on OSX

Fixes #858

Test against Ruby 2.2.6, 2.3.3, and 2.4.0

Fix default type on listen_to method_option for newer versions of Thor

Signed-off-by: Rémy Coutable <remy@rymai.me>

Execute the codeclimate-test-reporter bin as a separate CI step

Signed-off-by: Rémy Coutable <remy@rymai.me>

Rework logging and UI configuration