fix typo of CHANGELOG

CHANGELOG.md

@@ -40,7 +40,7 @@ let style = Style::default().modifier(Modifier::ITALIC | Modifier::BOLD);
 
 ## v0.4.0 - 2019-02-03
 
-### Added
+### Added
 
 * Add a new canvas shape: `Rectangle`.
 * Official support of `Crossterm` backend.
@@ -49,11 +49,11 @@ let style = Style::default().modifier(Modifier::ITALIC | Modifier::BOLD);
 * The gauge widget accepts a ratio (f64 between 0 and 1) in addition of a
 percentage.
 
-### Changed
+### Changed
 
 * Upgrade to Rust 2018 edition.
 
-### Fixed
+### Fixed
 
 * Fix rendering of double-width characters.
 * Fix race condition on the size of the terminal and expose a size that is