Bump up version to 0.28.0.

HyukjinKwon · HyukjinKwon · commit 42944e358a74 · 2020-02-27T22:42:49.000+09:00
diff --git a/databricks/koalas/version.py b/databricks/koalas/version.py
@@ -14,4 +14,4 @@
 # limitations under the License.
 #
 
-__version__ = "0.27.0"
+__version__ = "0.28.0"

Original file line number	Diff line number	Diff line change
`@@ -14,4 +14,4 @@`
`14`	`14`	`# limitations under the License.`
`15`	`15`	`#`
`16`	`16`
`17`		`-__version__ = "0.27.0"`
	`17`	`+__version__ = "0.28.0"`