[DOC] Doc improvements (#266)

* Doc improvements to mode setting

* Update changelog with PR number

* Rebase against master

Author: karenzone

Diff for: CHANGELOG.md

@@ -1,6 +1,9 @@
 ## 4.1.17
-  - Added configuration setting `check_archive_validity` settings to enable gzipped files verification, 
-  issue [#261](https://github.com/logstash-plugins/logstash-input-file/issues/261)
+  - Added configuration setting `check_archive_validity` settings to enable
+  gzipped files verification, issue
+  [#261](https://github.com/logstash-plugins/logstash-input-file/issues/261)
+  - [DOC] Added clarification for settings available with `read` mode [#235](https://github.com/logstash-plugins/logstash-input-file/pull/235)
+  - [DOC] Rearranged text and fixed formatting for `mode` setting [266](https://github.com/logstash-plugins/logstash-input-file/pull/266)  
 
 ## 4.1.16
   - Added configuration setting exit_after_read to read to EOF and terminate

Diff for: docs/index.asciidoc

@@ -370,16 +370,17 @@ A default of 4095 is set in internally.
 
 What mode do you want the file input to operate in. Tail a few files or
 read many content-complete files. Read mode now supports gzip file processing.
-If "read" is specified then the following other settings are ignored:
 
-. `start_position` (files are always read from the beginning)
-. `close_older` (files are automatically 'closed' when EOF is reached)
+If `read` is specified, these settings can be used:
 
-If "read" is specified then the following settings can be used:
+* `ignore_older` (older files are not processed)
+* `file_completed_action` (what action should be taken when the file is processed)
+* `file_completed_log_path` (which file should the completed file path be logged to)
 
-. `ignore_older` (older files are not processed)
-. `file_completed_action` (what action should be taken when the file is processed)
-. `file_completed_log_path` (which file should the completed file path be logged to)
+If `read` is specified, these settings are ignored:
+
+* `start_position` (files are always read from the beginning)
+* `close_older` (files are automatically 'closed' when EOF is reached)
 
 [id="plugins-{type}s-{plugin}-path"]
 ===== `path`