CocoaPods Private Repo support (#107)

Summary:
This PR brings us one step closer for publishing SonarKit.podspec to the public Cocoapods master repository. This solves [#93](https://github.com/facebook/Sonar/issues/93).

- [X] `SonarKit.podspec` now lints by passing the `--sources` flag and the `--use-libraries` flag. `pod spec lint  SonarKit.podspec --sources=https://github.com/facebook/Sonar,master --allow-warnings --use-libraries` Same for `pod repo push`.

- [X] `SonarKit.podspec` is now also published to the CocoaPods Private repo. What does this mean? It means that we no longer need to manually define all of `SonarKit` dependencies in the Podfile. It only takes `SonarKit` consumers to add this line `source 'https://github.com/facebook/Sonar.git'` on top of any Podfile, and `SonarKit` will be installed by just defining it with `pod SonarKit`.

- [X] We are publishing a Cocoapods Private Repo in the meantime we don't have all of our dependencies updated and published to the CocoaPods master repo. The CocoaPods Private Repo contains updated dependency podspecs that will need to be published to the CocoaPods master repo in the near future. That will be the next action item in order to have SonarKit.podspec published as well.

- [X] Sample App Podfile has been refactored, much simpler and cleaner.

- [X] SonarKit Framework project now pulls its dependencies from the cocoapods master repository and the temporary private repository instead of the local podspecs. I am able to compile the SonarKit framework project now, before I was unable to.

- [X] Local third party podspec dependencies have been removed.

emilsjolander priteshrnandgaonkar noahsark769 feel free to contribute or expose any concerns.
Closes https://github.com/facebook/Sonar/pull/107

Reviewed By: danielbuechele

Differential Revision: D8694271

Pulled By: priteshrnandgaonkar

fbshipit-source-id: dcccf70d917cad1e27606a29c0b921883bf9a76f

Specs/PeerTalk/0.0.2/PeerTalk.podspec

@@ -0,0 +1,16 @@
+Pod::Spec.new do |spec|
+    spec.name     = 'PeerTalk'
+    spec.version  = '0.0.2'
+    spec.license  = { :type => 'MIT' }
+    spec.homepage = 'http://rsms.me/peertalk/'
+    spec.authors  = { 'Rasmus Andersson' => 'rasmus@notion.se' }
+    spec.summary  = 'iOS and OS X Cocoa library for communicating over USB and TCP.'
+
+    spec.source   = { :git => "https://github.com/rsms/peertalk.git" }
+    spec.source_files = 'peertalk/*.{h,m}'
+    spec.requires_arc = true
+    spec.ios.deployment_target = '8.4'
+    spec.osx.deployment_target = '10.10'
+
+   spec.description = "                    PeerTalk is a iOS and OS X Cocoa library for communicating over USB and TCP.\n\n                    Highlights:\n\n                    * Provides you with USB device attach/detach events and attached device's info\n                    * Can connect to TCP services on supported attached devices (e.g. an iPhone), bridging the communication over USB transport\n                    * Offers a higher-level API (PTChannel and PTProtocol) for convenient implementations.\n                    * Tested and designed for libdispatch (aka Grand Central Dispatch).\n"
+end