changelog markdown "fix" for versions

CHANGELOG.md

@@ -1,37 +1,37 @@
-## 2016_06_18_1
+## `2016_06_18_1`
 
 * `android-24` is no longer preview - package names were changed
 
 
-## 2016_05_29_1
+## `2016_05_29_1`
 
 * Install `Gradle` from official APT repo, instead of from a PPA
 * Install `Maven` from official APT repo, instead of from a PPA
 * Java (OpenJDK) upgrade from 7 to 8
 
 
-## 2016_05_26_1
+## `2016_05_26_1`
 
 * "Checkpoint", before migration to `ubuntu:16.04`
 * Based on `bitriseio/docker-bitrise-base:2016_05_14_1`
 
 
-## 2016_04_09_1
+## `2016_04_09_1`
 
 * `fastlane` pre-installed
 
-## 2016_03_17_1
+## `2016_03_17_1`
 
 * Restructured `Dockerfile` (Android package install related codes), to fix
   Android package install license acceptance issues.
 * `system_report.sh` now tests whether `adb` is available, prints it's version
   and lists the content of `platform-tools`, to check whether the platform-tools
   package was installed correctly
 
-## 2016_03_11_1
+## `2016_03_11_1`
 
 * `android-N` and `build-tools-24.0.0-preview` packages pre-installed
 
-## 2016_01_09_1
+## `2016_01_09_1`
 
 * `build-tools-23.0.1` is now pre-installed