Support node 6+ only

Author: mathiasrw

.travis.yml

@@ -1,10 +1,8 @@
 language: node_js
 node_js:
   - "node"
+  - "7"
   - "6"
-  - "5"
-  - "4"
-  - "0.12"
 
 script:
   - npm run test-cli

README.md

@@ -198,7 +198,7 @@ Display manual. (can be given as only argument)
 
 ### Limitations
 - RexReplace reads each file fully into memory, so working on your 4Gb log files will probably not be ideal.
-- For versions of Node prior to 0.12, please use [the legacy version of RexReplace called rreplace](https://www.npmjs.com/package/rreplace)
+- For versions of Node prior to 6, please use version 2.2.x. For versions of Node prior to 0.12, please use [the legacy version of RexReplace called rreplace](https://www.npmjs.com/package/rreplace)
 
 ### Quirks
 - Per default `€` is treated as an alias for `$` in the CLI input. The main reason is for you not to worry about how command line tools often have a special relationship with the `$` char. Your can escape your way out of this old love story, but it often pops up in unexpected ways. Use the `-€` flag if you need to search or replace the actual euro char. 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "rexreplace",
-  "version": "2.3.0",
+  "version": "2.3.1",
   "description": "Flexible CLI regex replace in files.",
   "author": "Mathias Rangel Wulff",
   "license": "MIT",