Issue #56: Fix `NullPointerException` when deleting cards
Issue #56: Fix clear filter
Testing: Clean up `assertListViewContainsItems()`
Testing: Change `mActivity` to a local variable `activity`
Testing: More tests using FEST
Remove XML project files
Merge branch 'android/studio' into issue/56-loaders
Remove XML files from .idea folder
Merge pull request #305 from codeguru42/android/tests

Android/tests
Merge pull request #306 from codeguru42/android/cleanup

Remove XML files from .idea folder
Remove XML files from .idea folder
Merge pull request #307 from codeguru42/android/cleanup

Remove XML files from .idea folder
Add Crashlytics integration
Disable Crashlytics reporting for debug builds
Ignore a file with Crashlytics settings
Use `OnCheckedChangeListener`s instead of `OnClickListener`s
Merge pull request #311 from codeguru42/android/crashlytics

Add Crashlytics integration
Merge pull request #313 from codeguru42/android/oncheckedchangelistener

Use `OnCheckedChangeListener`s instead of `OnClickListener`s
Update API and library versions

Updated to use API 20. Cannot use API 21 yet as there is an issue with the tests when
using appcompat-v7:21.0.0.
Add ButterKnife dependency