Update for PureScript 0.11

[garyb]

No description provided.

[sudhirvkumar]

@garyb this PR can also be merged?

[garyb]

Not quite, there's some changes to come yet.

[garyb]

@paf31 Ok, just pushed a pretty big update...

• Dropped IsForeign as discussed variously
• Removed the newtypes for null / undefined / etc in favour of just providing functions that can be specific about what they read instead - the newtypes only existed to guide the chosen IsForeign implementation before.
• Removed parseJSON since that's highly misleading about what this library is for (it exists in altered from in support code for the examples though, as it makes them easier to read rather than having the example values being parsed in a separate JS file in each case)
• Added a new !! operator that allows chaining of property reads, so you can do value ! prop1 !! prop2
• Updated all of the examples accordingly

[paf31]

One thought: we could overload ! using a type class here.

[paf31]

Looks good! I will probably continue to maintain some of the JSON features in the more opinionated foreign-generics but I think these are the right choices for this library.