Update build tools to 0.10 / gradle to 1.12

1.
Fixes bug caused by chrisbanes/gradle-mvn-push having moved to android gradle plugin 0.10+
while this library remained at older version.

The android.plugin.getRuntimeJarList() no longer worked.

https://github.com/chrisbanes/gradle-mvn-push/commit/44a1e74d01afd31ae1b78e6d85d1ab992295bb82

2.
Build tools were updated to more recent 0.10 and took the opportunity and
updated gradle as well.

3.
Also no longer using the old raw.github.com domain to get the
chrisbanes/gradle-mvn-push gradle script.
Now using the newer githubusercontent.com.

More info:
https://developer.github.com/changes/2014-04-25-user-content-security/