Using xml2js and add xml namespace test

node-xm2json give parser error with xml
that have namespace prefix (:). In this test,
I include Android repository real xml as example.
Make Travis happy
Add pretty print option.

See xml2js README for available options
Support YAML

Currently we convert to JSON first and convert to YAML format
Refactoring
YAML to JSON
Small prettyfication
JSON to YAML
Update README for options
Refactoring

Source converted to JSON format for default. Source type checked from
file extension.

 - XML > JSON
 - XML > YAML
 - JSON > YAML
 - YAML > JSON
Remove unused module
Merge pull request #1 from hariadi/master

Support YAML