Updated to Android Studio 0.8.1 and LineView point selection fix

c0f12b25693e3eb91fd0091ef8584c5446942266

__Lastest Android Studio version is `0.8.1`, so I updated project settings to work with new IDE.__

  - Changed `builTools` vesion to `19.1.0`.
  - Changed `targetSdk` version to `19`.
  - Changed `android gradle plugin` version to `0.12.+`.
  - Changed `gradle` verstion to `1.12`.
  - Fixed `release buildType` for library `build.gradle`.
  - Added `build/` to root `.gitignore`.


ba8502d8b3aeafd3c0adc2c140c8bcd2f06884dc :

__Previously selected point on LineView changed on every touch. And view had issue with scrolling that looks like this:__

![LineView before]

__It's not expected behavior, as for me. So I fixed this, added some optimizations and now it looks like this:__

![LineView now]

[LineView before]: https://lh4.googleusercontent.com/s-UqsvfyGttuji_3cSYjcVHwphYxQELtx97Fxi1zpUWSal9Xiz9IPdPh_rMlIiua7UfAOHstgAY
[LineView now]: https://lh6.googleusercontent.com/GtoSZ6Tqc2RtUZO7PvHAMlCH6EYxF6QCOSR0Mnq1f7gMrs-tPC6PEGWRb3KUHqFkmwJFw56f0rY