Adds documentation to fix #135
Remove support for Ruby 1.8.7

Ref: #193

We no longer support 1.8.7 and will no longer run the Travis test suite on 1.8.7
Add Travis support for 2.0.0

Ref #194

Let's see what happens with these tests
Add rake task to print out version info
Add debugging to Travis
Attempt to see where wkhtmltopdf is being installed
Toy with using apt
Let's see if the gem is the issue
Re-add the gem dependency

Actually print the version info
One more stab at fixing Travis
Specify a version that Ubuntu actually has a package for
Try using heroku gem on Travis
Remove `before_script` in .travis.yml
I am going to hate myself
Don't require the wkhtmltopdf gem

It can be added/gem installed as needed. Also sort dependencies :).

One possible issue: will it need to be added to the gemfile/gemspec for
it to be picked up when running rake? Or will you be able to just `gem
install wkhtmltopdf`?