Fix bug in fragment implementation

On a configuration change, or any other event which causes the `MainActivity` to be
recreated, an instance of `BaseballCardList` is added over the current fragment.
This commit fixes this issue.
Merge branch 'devel/android' into bug/fragments

Conflicts:
	gradle/android/src/main/java/bbct/android/common/activity/MainActivity.java
Merge pull request #282 from codeguru42/bug/fragments

Bug/fragments