Don't use peerDependencies

[Soreine]

As pointed out here GitbookIO/slate-edit-table#59 (comment)

It would be simpler to have these as dependencies:

"eslint-plugin-flowtype": "^2.41.0",
"eslint-plugin-jsx-a11y": "^5.1.1",
"eslint-plugin-prettier": "^2.4.0",
"eslint-plugin-react": "^7.5.1",
"prettier": "^1.9.2", 

[zhouzi]

I was about to submit a PR but noticed the dependencies have been recently moved out of "dependencies" to "peerDependencies" by @SamyPesse in 477692b

@SamyPesse should they remain as peer dependencies?

Also, the package.json currently has two peerDependencies entries.

[SamyPesse]

If I recall correctly, it's not working well with ESlint to have those as dependencies of the config. ESlint wanted those module as first-level dependencies.

It may has changed.