MAINT bump version to 3.1.0, update changelog

CHANGELOG.md

@@ -6,6 +6,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
 
 ## [Unreleased]
 
+### Added
+### Changed
+### Deprecated
+### Removed
+### Fixed
+### Security
+
+## [3.1.0] - 2021-02-21
+
 ### Added
 * Part-of-speech tagging:
    - Added the function `pos_tag` that takes a segmented sentence or phrase
@@ -17,9 +26,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
    - Improved segmentation quality by revising the underlying wordlist data.
 * The test suite now covers code snippets in both the docstrings and `.rst` doc files.
 
-### Changed
-### Deprecated
-### Removed
 ### Fixed
 * Fixed the issue of not opening text files with UTF-8 encoding
   (a possible issue on Windows).
@@ -28,8 +34,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
 * The word segmentation function `segment` now strips all whitespace
   from the input unsegmented string before segmenting it.
 
-### Security
-
 ## [3.0.0] - 2020-10-25
 
 ### Added

setup.py

@@ -5,7 +5,7 @@
 
 _THIS_DIR = os.path.dirname(__file__)
 
-_VERSION = "3.1.0.dev3"
+_VERSION = "3.1.0"
 
 
 def _get_long_description():