Release types on npm

[ScreamingHawk]

I'm using solc in a typescript project but typings are not exported in the npm package. Please consider updating the package release to include the typings.

[ScreamingHawk]

Related to #287

[roninjin10]

Looks like this is a pretty light lift to include the typings. All we got to do is add the .d.ts files to the package.json field that includes specific files

[roninjin10]

Put up a pr for this here #693