Add ability to style row data by passing in style index value

ADDED: Row data will be styled according to the styleIndex param passed or will default to style index 0 which is referenced in the XML stylesheet.

FIXED: Fixed indentation in test file
Ignore .log and .xlsx files

UPDATED: Update .gitignore to ignore XLSX and LOG files
Updated README to indicate how to run tests

UPDATED: Updated README file to indicate how to run the unit tests for the library
Add travis build configuration file
Add test for bigger data set
Fixed error in test case
Update README to show build status
Markdown for build status in README
Get style index for row data from respective column settings
Update test to test with style indexes
use async library to execute async task

also updated travis.yml to send notifications to multiple email addresses on success and failure
Change file names in test cases