Add Arithemtic Ops and refactor Base Ops

Add these operators:
Addition
Ceil
Division
Exponentiate
Floor
Max
Min
Modulo
Negation
Subtraction

Add these Operator Classes:
UnaryOperator
BinaryOperator
MultipleOperator

Refactor All existing Operators to extend from one of those bases.
revert php version requirement
5.3 revert and .gitignore fix
revert composer.json version
add VariableOperator and ProposistionOperator
revert Yoda conditions; clean up doc blocks
remove magic from constructor; make sure VariableOperatnds return values
update some doc blocks
fix to rule builder fluency
initial implementation of set operators
add containsSubset Operator
add case insenstive string comparison
Update for coding standard.
Merge remote-tracking branch 'ludicruz/develop' into feature/set-operators

Conflicts:
	src/Ruler/Operator/SetContains.php
	src/Ruler/Operator/StringContains.php
	src/Ruler/Value.php
Minor coding standard fixes.
Refactor RuleBuilder set operator methods

Extract common functionality into private helper method.
Update docblocks for Set.
Restore Contains operator, but deprecate it.

Defer to StringContains or SetContains, trigger an E_USER_DEPRECATED with a helpful message.
Add StartsWith, EndsWith comparison operators
Merge pull request #26 from gogume/starts-ends-with

Add StartsWith, EndsWith comparison operators