Set up Maven packaging and Bintray upload (#104)

Summary:
This make use of the the setup we have at Litho, which should make
it easier to keep them in sync.

It creates proper source jars, AARs (without bundling in unwanted
transitive deps) and POMs.
Closes https://github.com/facebook/Sonar/pull/104

Reviewed By: priteshrnandgaonkar

Differential Revision: D8638912

Pulled By: passy

fbshipit-source-id: ff4921c0683e9b6f859085b542ceae840a7e8291

android/build.gradle

@@ -1,5 +1,5 @@
 apply plugin: 'com.android.library'
-
+apply plugin: 'maven'
 apply plugin: 'de.undercouch.download'
 
 import de.undercouch.gradle.tasks.download.Download
@@ -253,4 +253,11 @@ android {
 
 project.afterEvaluate {
     preBuild.dependsOn prepareAllLibs
+
+apply from: rootProject.file('gradle/release.gradle')
+
+task sourcesJar(type: Jar) {
+    from android.sourceSets.main.java.srcDirs
+    classifier = 'sources'
 }
+artifacts.add('archives', sourcesJar)}