Update Utils.java

#424242 (android 5) / #303030 (android 4) is more gentle than black + fits in the the new dark material appCompat.

Added a space between title and content (were squished together).

Below is another mockup that changes title and positive/negative button text. Cleaner, no?

Android 5
![device-2014-12-16-215124](https://cloud.githubusercontent.com/assets/4555882/5465861/c2dc5866-856d-11e4-999b-0b1eaf32c1c8.png)

Android 4
![device-2014-12-16-221530](https://cloud.githubusercontent.com/assets/4555882/5466049/187744cc-8571-11e4-8f7d-617a475f459b.png)