Minor warning fixes
Ignore xcode user files
Set path to find doxygen in /usr/local/bin; ignore docs
Update build settings
Fix minor cyclic dependency warning
Requesting empty subsets causes nil arg exceptions

Added test cases for subsetFromObject:toObject:... that demonstrate the problem
and validate other empty selections. Check to make sure anObject is still valid
after finding our start position.
Merging 'mbauman/master'

Conflicts:
	.gitignore
Fixing indentation and formatting.
static analyzer minor fixes

Conflicts:
	source/CHAbstractBinarySearchTree.m
added skip install to iOS library project
Fixing more indentation and formatting.
Making the static analyzer happy.
Project touched by Xcode 5.
Fixed CHMutableDictionary to be ARC compatible
Fixed framework search paths for CHDataStructures-iOS project. Fixed CHBinaryTreeNode, CHSinglyLinkedListNode, and CHDoublyLinkedListNode object to be __unsafe_unretained for use with ARC. Removed hidden visibility for kCHPointerSize as the symbol was being duplicated in dependent projects.