Remove redundant modifiers in interface method declarations

As per JLS it is discouraged to specify the public modifier for methods
declared in an interface. This commit also makes sure that the behavior is
consistent across code files.
Merge pull request #285 from cameoh/remove-redundant-modifiers

Remove redundant modifiers in interface method declarations
enable hiding listview item,ex. toggle off items in group
upgrade buildToolVersion
Merge pull request #296 from lsjwzh/master

enable hiding listview item,ex. toggle off items in group
fixes #115
Added ability to set sticky header offset from top. Fixes #146
bumped version
obvious fix for header click handler

if user do not provide "OnHeaderClickListener", the header view will not be clickable,
so user will be able to "get" to the underlying views and handle clicks by himself
add ExpandableStickyListHeaderListView which enable listview to expand/collapse sub items
Update gradle and fix some formatting
Make sure to clear sticky header when at top
Bump version
addFooterView(View v, Object data, boolean isSelectable) is missing
Merge pull request #1 from emilsjolander/master

sync with master
add ExpandableListTestActivity
Merge remote-tracking branch 'origin/master'
simplify IAnimationExecutor
update ExpandableListTextActivity
fix divider height calculate logic when collapse items