Update .travis.yml and readme with badge

.travis.yml

@@ -8,8 +8,6 @@ cache:
 
 # Run tests against all these PHP versions
 php:
-  - 5.4
-  - 5.5
   - 5.6
   - 7.0
   - 7.1

Readme.md

@@ -1,6 +1,8 @@
 PHP Markdown
 ============
 
+[![Build Status](https://travis-ci.org/michelf/php-markdown.svg?branch=lib)](https://travis-ci.org/michelf/php-markdown)
+
 PHP Markdown Lib 1.8.0 - 14 Jan 2018
 
 by Michel Fortin
@@ -163,10 +165,12 @@ potential side effects, and future extensibility -- before deciding on
 acceptance or rejection.
 
 If you make a pull request that includes changes to the parser please add
-tests for what is being changed to [MDTest][] and make a pull request there
-too.
+tests for what is being changed to the `test/` directory. This can be as
+simple as adding a `.text` (input) file with a corresponding `.xhtml`
+(output) file to proper category under `./test/resources/`.
 
- [MDTest]: https://github.com/michelf/mdtest/
+Traditionally tests were in a separate repository, [MDTest](https://github.com/michelf/mdtest)
+but they are now located here, alongside the source code.
 
 
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