Added the arithmetic function contracts and some general helper functions that they use.
Added power operator and fixed sub and add operators to work with vectors
Removed print statement lines
Changed contract to allow contracts to be executed after an assertion fails.
Fixed up contracts so that they are properly called and changed from comments. Still need to do coersion and fix loops.
Refactoring and adding coercion for basic arithmetic. Still have a problem with constant arguments when certain object args are passed in.
Removed the require non-empty result as it no longer makes sense
Merge pull request #12 from isupeene/arithmetic_contracts

Arithmetic contracts. Constant arguments when using coerced objects still not working right.
Update .gitignore
Added vector contracts and test cases from the Ruby source code.
Removed unused method.
Removed another unused method.
Removed unnecessary handling of numerics in op_subtract_postcondition for the VectorContract.
Merge branch 'vector' of github.com:isupeene/sparse-matrix into vector

Conflicts:
	src/contracts/vector_contract.rb