Feature/object data parsing (#18)

- This update is to make testing easier and add new functions with fewer dependencies.

- I removed all JSONObject based parsing codes. Instead, I added a JSON library, called Moshi (https://github.com/square/moshi). This lets the network library, Retrofit, parse the response data into java objects such as PXLPhoto.

- Circular dependencies are removed

- I removed Context from Data classes such as PXLPhoto, PXLAlbum, PXLPdpAlbum. In Android unit tests, using non-Android classes can speed up the testing runtime.

- More unit tests for network error cases

.gitignore

@@ -1,9 +1,68 @@
+# Built application files
+*.apk
+*.ap_
+
+# Files for the ART/Dalvik VM
+*.dex
+
+# Java class files
+*.class
+
+# Generated files
+bin/
+gen/
+out/
+
+# Gradle files
+.gradle/
+build/
+
+# Local configuration file (sdk path, etc)
+local.properties
+keystore.properties
+pixleekey.properties
+
+# Proguard folder generated by Eclipse
+proguard/
+
+# Log Files
+*.log
+
+# Android Studio Navigation editor temp files
+.navigation/
+
+# Android Studio captures folder
+captures/
+
+# IntelliJ
 *.iml
-.gradle
-/local.properties
-/.idea/workspace.xml
-/.idea/libraries
-.DS_Store
-/build
-/captures
+.idea/workspace.xml
+.idea/tasks.xml
+.idea/gradle.xml
+.idea/assetWizardSettings.xml
+.idea/dictionaries
+.idea/libraries
+.idea/caches
+
+# Keystore files
+# Uncomment the following line if you do not want to check your keystore fil
+\es in.
+#*.jks
+
+# External native build folder generated in Android Studio 2.2 and later
 .externalNativeBuild
+
+# Google Services (e.g. APIs or Firebase)
+google-services.json
+
+# Freeline
+freeline.py
+freeline/
+freeline_project_description.json
+
+# fastlane
+fastlane/report.xml
+fastlane/Preview.html
+fastlane/screenshots
+fastlane/test_output
+fastlane/readme.md  ₩