refactor ec2-set-dme-dns.rb to more closely follow ruby coding practices

[bgupta]

1. All URLs to Class Variables
2. All the authentication tokens to instance variables
3. Put everything in a CNameRecord Class
4. Most of the code below the require statements but above load_properties could be put under "def initialize" in a CNameRecord Class.
5. Break the code into two files. A library and the script that calls the library. (Note I will probably still keep a single file version for ease of deployment).