fixing peerDependency to work with React 15+

[igorsantos07]

Yet another PR that's probably gonna get forgotten here, just like react-d3/react-d3-basic#43

[nmqanh]

Yeah I think this one should be updated and published!

[vartika-skyport]

@igorsantos07 , did you test the pull request?
On applying your changes locally, following errors were generated. Would you check and resolve these as this will otherwise break the library.

$ npm install
npm WARN package.json react-d3-core@1.3.9 No repository field.
npm WARN package.json react-d3-core@1.3.9 license should be a valid SPDX license expression
npm WARN peerDependencies The peer dependency react included from react-d3-core will no
npm WARN peerDependencies longer be automatically installed to fulfill the peerDependency
npm WARN peerDependencies in npm 3+. Your application will need to depend on it explicitly.
npm WARN peerDependencies The peer dependency react-dom included from react-d3-core will no
npm WARN peerDependencies longer be automatically installed to fulfill the peerDependency
npm WARN peerDependencies in npm 3+. Your application will need to depend on it explicitly.
npm ERR! Darwin 13.4.0
npm ERR! argv "/usr/local/bin/node" "/usr/local/bin/npm" "install"
npm ERR! node v4.6.1
npm ERR! npm v2.15.9
npm ERR! code EPEERINVALID

npm ERR! peerinvalid The package react@15.0.2 does not satisfy its siblings' peerDependencies requirements!
npm ERR! peerinvalid Peer react-faux-dom@2.5.0 wants react@*
npm ERR! peerinvalid Peer react-addons-test-utils@0.14.8 wants react@^0.14.8
npm ERR! peerinvalid Peer react-dom@0.14.8 wants react@^0.14.8
npm ERR! peerinvalid Peer react-bootstrap@0.28.5 wants react@>=0.14.0
npm ERR! peerinvalid Peer react-router@2.4.0 wants react@^0.14.0 || ^15.0.0
npm ERR! peerinvalid Peer babel-preset-react-hmre@1.0.1 wants react@^0.14.1