Added Travis integration

This is how I originally set up Travis integration for our GitHub repos. It's based off of [R Travis](https://github.com/craigcitro/r-travis/). So the step involved are as such:

Add a `.travis.yml` file to the repo. Here we establish what needs to be installed. It basically installs all dependencies assuming they are available on CRAN. You can also install packages that exist only on GitHub like so:

```
- ./travis-tool.sh github_package assertthat
```

Note: We no longer have to do this for `assertthat`.

I also created an encrypted API key to add to the yml file so we have notifications in the Package Development room of our HipChat. Usually build pass/fail notifications go there. Especially useful if you want to turn off extraneous email notifications.

Then we have to turn on Travis integration on [Travis CI](https://travis-ci.org/). I already did that for rEML now but you can do it too. I think if you just sign on with your GitHub account, it shows all repos and organizations you have access to.

Finally, from the Travis page for a repo, you can grab the build shield from the top right of the screen. I've added it to the README.
Merge branch 'master' of github.com:ropensci/reml
Literature module and testing improvements

o Improves the generic literature coercion
  o improves the automatic detection of coercion types to eml

o Finishes up literature testing
  - Renames the test file for literature to fix typo
  - Adds test for the rest of literature module coercions
    and auto detections

o belongs to issue #27
Includes the literature module where it can occur

Belongs to issue #27
Merge pull request #89 from cpfaff/litrature

Litrature
editing constructor for eml, avoid defining ID in eml prototype as the id is then not unique byt re-used through-out the session
merge
whoops, regenerate README
Fixes #88 upstream (inst/doc/README.Rmd)
fix typo in uuid use
debugging person coercions
fixing up test cases after changes to interface
fix broken test with id
fix typo in test: a_audioVisual should have been an_audioVisual
flush out methods module
eml_write support additional arguments to dataset via ...
flush out methods module, add ListOfcitation to literature module
allow methods to be given as plain-text
update tutorial
updated README