Fixed bootstrap build error to download dependencies

Below is error message. 

[ERROR] Failed to execute goal on project bootstrap: Could not resolve dependencies for project io.appium.android:bootstrap:jar:1.0.0-SNAPSHOT: The following artifacts could not be resolved: android:android:jar:4.3_r1, android.test.uiautomator:uiautomator:jar:4.3_r1: Could not find artifact android:android:jar:4.3_r1 in central (http://repo1.maven.org/maven2) -> [Help 1]