Fix Travis Build Issues

[lobopraveen]

• Changed language from go to minimal
• Fixed how hugo was being downloaded and installed as it started failing recently
• Introduced HUGO_VERSION to fix deploy updates all published files due to version #24
• Redid .travis.yml so that it can be reused by others just by switching the environment variable. This will help if the repo is forked
• Removed hard coded user name, repo slug etc.
• Added check to skip deploy (committing the code and pushing back to repo) if there are no changes. Closes Travis CI fails when there are no changes #59
• Cleaned up the publish.sh script
• Build time dropped from just under 4 minutes to under 30 seconds
• Fix pull request builds - fixes Pull requests are not getting built #62