Add CocoaPods support

[dkhamsing]

Hey, this pull request would close #2

• create podspec
• podspec passes lint

dkhamsing$ pod --version
0.39.0

dkhamsing$ pod spec lint PMJSON.podspec 

 -> PMJSON (0.9)

Analyzed 1 podspec.

PMJSON.podspec passed validation.

• simple test demo project https://github.com/dkhamsing/PMJSON/tree/cocoapods-demo/CocoaPodsDemo

import PMJSON

let jsonString = "{\"id\":88}"
print(jsonString)
do {
    let json = try JSON.decode(jsonString)
    print (json)
} catch _ {
    print ("sad")
}             

{"id":88}
["id": JSON.Int64(88)]

• get setup with CocoaPods Trunk service (to publish/make it public) @kballard https://guides.cocoapods.org/making/getting-setup-with-trunk.html
• update readme with text below @kballard

To install using CocoaPods, add the following to your Podfile:

pod 'PMJSON', '~> 0.9'

[lilyball]

Hi @dkhamsing, I apologize for not seeing this earlier. Thanks for the pull request, I'll get it merged in shortly.

[dkhamsing]

🎉