Renamed regex_t to onig_regex_t to prevent conflicts

It seems that with Swift and iOS 8, the typedef regex_t conflicts with
an existing typedef in the iOS8 SDK
(/Applications/Xcode6-Beta5.app/Contents/Developer/Platforms/iPhoneSimul
ator.platform/Developer/SDKs/iPhoneSimulator8.0.sdk/usr/include). With
Objective-C, it has no problems compiling, but there must be a bug in
the Swift compiler there is an issue which causes the names to conflict.
Added helper function to compare ranges

XCTAssertEqual cannot compare ranges anymore, so I added a helper
function to compare the ranges.
Changed SenTestingFramework library link

The link was broken, so I fixed it. Changing the SenTestingKit to
optional allows the tests to run and pass.