Feature/xctest

I replaced SenTest with XCTest. 
I cleaned up the FRAMEWORK_SEARCH_PATHS to not to contain some junk, please reference https://github.com/seivan/CocoaSPDY/compare/twitter:develop...feature%2Fxctest?expand=1#diff-607867dba70c420bf87de2f213acf3afR761

I changed the deployment target to 7 for making sure the XCTest run.

However, I can't seem to get the actual tests to run. I just get an exit with 0, which means it does run the library but that's the end of it. It doesn't actually run the suite, *care to throw some eyes on this?*
https://travis-ci.org/twitter/CocoaSPDY/builds/15848795#L578




Now, I'd like to suggest getting rid of pre-built static frameworks for several reasons

* You can still drag and drop a folder of source code as you could with pre-built static frameworks. 
* It allows for easier 'hotfixes' and promotes contributions
* It allows for a better work flow for the maintainers, just set a local path for the pods/source and edit the sample/tests and it will reflect the changes directly. 
* You will work/test against the source/'pod' that the users of the library use. 
* You can run your test suites against forks of the pod for testing problems/bug reports easier. 
* It doesn't requiring pre-built frameworks
* It doesn't requiring updating for new architectures
* It allows for better debugging options




Basically what I'm suggesting is doing local path (like bundler for ruby).

Let me know if you want a sample, I've done it for several libraries, and I could easily do a branch for demonstration here, but it also requires that we get rid of the static pre-built frameworks that honestly lacks any benefits compared to source code.