Various fixes

Mainly exposed by updating the showcase application
haxelib
allow icon of button to fill whole button with iconPosition="fill"
Updated gradient_mobile theme
corrected sliding directory for Stack
added history to stack and function to go back
Added functions to client to return the dimensions of the window
Merge pull request #103 from RudolfVonKrugstein/gradient_mobile

Updated gradient_mobile theme
Merge pull request #104 from RudolfVonKrugstein/iconfill

allow icon of button to fill whole button with iconPosition="fill"
Merge pull request #105 from RudolfVonKrugstein/stack

Stack
Merge pull request #106 from RudolfVonKrugstein/window_dim

Added functions to client to return the dimensions of the window
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' of https://github.com/mikedotalmond/haxeui