Promise Support and misc refactor

#115 - Add promise support to fetchr

// Before
fetcher
    .read('data_api_service')
    .params({id: ###})
    .end(function (err, data) {
        // data is returned by `data_api_service`
    });
//After
fetcher
    .read('data_api_service')
    .params({id: ###})
    .end()
    .then(function (result) {
        // result.data is returned by `data_api_service`
    });

#122 - Refactor service metadata

Metadata logic in fluxible-plugin-fetchr has been moved into fetchr itself. The usage is the same as before.

// callback
fetcher
    .read('data_api_service')
    .params({id: ###})
    .end(function (err, data, meta) {
        // meta will contain any headers returned by the `data_api_service`
    });
// promise
fetcher
    .read('data_api_service')
    .params({id: ###})
    .end()
    .then(function (result) {
        // result.meta will contain any headers returned by the `data_api_service`
    });

Context picker support

#121 - Provide additional options contextPicker to determine how to pick the context values as parts of uri queries

Bugfix: Don't cast big integers into Numbers

• #120 Don't cast big integers into Number type

  Fetcher middleware receives all params as strings. It then, tries to cast these strings into their primitive types. However, numbers larger than MAX_SAFE_INTEGER were being rounded incorrectly introducing errors(See #119). The fix is to just leave these big integers as strings and let the user convert them as needed.

Added ability to return more information in error object

Thanks @KATT for the contribution!

An additional output property can be added to the error object to return addition information when an error occurs.

Provide function to update options

#114 - provide function to update options

Interface Changes

#110 - New CRUD interface

We're deprecating the old interface:

fetcher.read('resource', {id: ###}, {}, function (err, data, meta) {
    // handle err and/or data returned from data fetcher in this callback
});

in favor of a cleaner, chainable, interface:

fetcher
    .read('resource')
    .params({id: ###})
    .end(function (err, data, meta) {
     // handle err and/or data returned from data fetcher in this callback
    });

Few things to keep in mind:

• Always start fetcher requests with one of the CRUD (create, read, update, or delete) methods.
• Then chain with params, body, or clientConfig in any order.
• Always end requests with the end method and provide a callback.

Note: This release does not affect how your data services are defined, it just provides a new way to access your services.

Remove X-Requested-With headers for CORS

#103 Remove X-Requested-With headers for CORS. Thanks @neilius.

Allow xhr timeout to be configured for all requests

New:
#107 - Allow xhr timeout to be configured for all fetchr requests. Thanks @escalona.

Misc:
#104 - Improve test coverage
#105 - Update devDeps

Backport: Parsing error JSON client side

Backporting #98, because #98 resolves a potential inconsistency introduced in #80(already backported).

Fix bug where isRegistered didn't handle sub-resources

#102