Merge pull request #53 from briangriffey/master

Added gradle build
added NPE guard for mAdapter
Merge pull request #55 from mingfai/master

added NPE guard for mAdapter
updated gitignore
Adapter null check on every access in onTouchEvent()

A previous pull request performed a null check only in one of the three accesses to the instance variable 'mAdapter' in the onTouchEvent() method, which can be null when a touch event occurs.
Merge pull request #56 from marcosalis/master

Adapter null check on every access in onTouchEvent()
Accessing local variable before nullcheck in getFirstChildAtColumn(int)

The local variable 'child' is accessed right before a null check (also reported by static analyzer tool FindBugs).
Merge pull request #57 from marcosalis/master

Accessing local variable before nullcheck in getFirstChildAtColumn(int)
Merge remote-tracking branch 'upstream/master'