Dialog can be showed or hidden with custom action
Added support for multiple recipients.
Slightly changed State API to properly support multiple recipients.
Added angle calculation methods to Vector2

Added two methods to the Vector2 class, allowing to calculate angle between two vectors, and not only between the x-axis.

I'm not using the standard acos solution, math explained here: http://geomalgorithms.com/vector_products.html

Since the dot product is the cosine of the angle between two vectors, and the 2d cross product (perp dot) is the sine of the same angle, plugging both on a `atan2(crs, dot)` call can give the angle on the full circle (-180~+180, instead of `acos(dot)` solution, which gives only 0~180) and also avoid the two sqrts involved in normalising the vectors.

Here's another explanation on the matter: http://johnblackburne.blogspot.com.br/2012/01/angle-between-two-vectors.html
Update Vector2.java

shouldn't have a conversion here
add failsafe display mode and isUsingFailsafeDisplay() methods for LWJGL
add semicolon
remove isUsingFailsafeDisplay method from Graphics interface
Made the map implementations Java 8 compliant.
NateS solution for ObjectMap and IdentityMap.
Bugfix for AnimationController

When an animation has 0 seconds duration (it's still, not moving) the AnimationDesc.update() would hang indefinitely. This should make each frame consume 1 loop, though I'm not sure if this is the best way to handle this. What do you guys think?
fill out Decal with convenience methods, remove redundant axes Vectors and use stock axes vectors instead
Merge remote-tracking branch 'upstream/master' into failed-display
Fixes #2170
Merge pull request #2171 from Gtoknu/patch-9

Bugfix for AnimationController
Make #2171 compile
Should at least loop once
fix error msg in scene2dui ProgressBar
Merge pull request #2175 from jrenner/progress-bar

fix error msg in scene2dui ProgressBar
Merge branch 'master' into failed-display