Add build status and pod badges

- [x] Set up Travis CI to build this project whenever new commits are pushed to the repo
- [x] Show badges of build status and current pod version in README.md

P.S. The CI badge requires this repo to be enabled for building by the project owner. Please have a look at  https://travis-ci.org/profile and switch on this project. The badge would look like: 

[![Build Status](https://travis-ci.org/bcylin/JASwipeCell.svg?branch=travis-ci)](https://travis-ci.org/bcylin/JASwipeCell)