Fix Gradle Dynamic Version linting warning

[alexanderdean]

Avoid using + in version numbers; can lead to unpredictable and unrepeatable builds
(com.jakewharton.sdkmanager:gradle-plugin:0.12.+)

7 }
8 dependencies {
9 classpath 'com.android.tools.build:gradle:1.0.0'
10 classpath 'com.jakewharton.sdkmanager:gradle-plugin:0.12.+'
11 }
12 }