Fix plugin utilities documentation

[aaronsofaly]

This PR fixes some issues with the plugin utilities documentation. http://chaijs.com/api/plugins/.

This is in reference to this issue on the chai-docs repo.

To summarize these commits:

• This adds a headline for the .inspect() method and adds "Default is false" for the showHidden param
• This updates some of the headlines to use h3's instead of h1's .getActual(), and .test()
• This adds periods before each method .addChainableMethod(), .addProperty() .expectTypes(), .flag(), .getActual(), .overwriteChainableMethod(), .overwriteMethod(), .overwriteProperty(), .test(), and .transferFlags()
• This removes the space between the method name and the opening parenthesis .addChainableMethod(), .addMethod(), .addProperty(), .objDisplay(), .overwriteChainableMethod(), .overwriteMethod(), and .overwriteProperty()

[keithamus]

This all looks great @aaronsofaly! Let's get this merged in.

[keithamus]

Just waiting to see if dependency-ci is going to spring into life...

[lucasfcosta]

Awesome job! Thank you very much!

[keithamus]

Just disabled dependency-ci for now to get this one in