adding support for setting the jsx pragma value via config

[dominicbarnes]

This fixes #80

Instead of taking the approach mentioned there, this turned out to be far less complicated, it basically adds a second config option to the react/jsx-uses-react rule:

[ 2, 'dom' ]

This causes dom to be used in place of React as the used variable. I've also included a test and updated the docs for the aforementioned rule.

Let me know if there's anything else we need to do to get this merged! :D

[coveralls]

Coverage remained the same at 94.46% when pulling 4822162 on dominicbarnes:jsx-pragma-config into 598ab38 on yannickcr:master.

[dominicbarnes]

Although outside the scope of this PR, the rule name jsx-uses-react is a confusing name considering that it simultaneously supports the JSX pragma and this new config.

I was thinking it could be named jsx-uses-var instead, although that could just be confused with the very similarly-named jsx-uses-vars. (then there's backward-compatibility to consider)

[yannickcr]

Thanks :)

But actually I'd prefer to keep the [1, {"pragma": "dom"}] format to be coherent with the other rules. Also, it allows us to add other options in the future without breaking anything.

[yannickcr]

Great!

Just some little things: can you make a Rule Options section and use the same format as the other rules for the config file example ?

You can see an example here: https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/jsx-sort-prop-types.md#rule-options

[dominicbarnes]

I'm done making those changes! Let me know if there are any other changes to make

[coveralls]

Coverage increased (+0.01%) to 94.47% when pulling 82b7063 on dominicbarnes:jsx-pragma-config into 598ab38 on yannickcr:master.

[yannickcr]

LGTM.

Thanks!