Rename methods for adding comments

* I have a feature branch that implements issue commenting. This commit
  renames methods in `PullRequest` and `GithubApi` in anticipation of the
  changes on my branch.
* Rename `PullRequest#add_comment` to `PullRequest#comment_on_violation`
* Rename `GithubApi#add_comment` to `GithubApi#add_pull_request_comment`
Allow a user to exclude certain JavaScript files

Allows a user to configure hound to ignore specified JavaScript files.
This follows the "jshintignore" convention. If a .jshintignore file is
found and the user has not overwritten the path in the hound
configuration, it will automatically be used.

Otherwise, a user can specify the path to a file which specifies which
files to exlude during linting.

Example configuration:

```yaml
java_script:
  enabled: true
  ignore_file: ".javascript_ignore"
```

.javascript_ignore
```
app/assets/javascripts/**.js
``
Access owner information from PullRequest
Custom thoughtbot configuration for linting

Use a different set of style guide configurations when linting
thoughtbot specific repositories. This allows thoughtbot specific
projects to follow the thoughtbot styleguide closely as it is
updated without introducting changes without notice to paying customers.
Synchronize with master
Move thoughtbot-specific styles