Added ability to set defaultEngine for the express app.

Will default to js
//usage
var server = new Server({defaultEngine: 'coffee'});
Updated pull request based on good ideas expressed by dominikkrejcik
in https://github.com/airbnb/rendr/pull/95
Merge pull request #132 from givingstage/default_engine_for_express

Added ability to set defaultEngine for the express app.
Adding example of how to set up sessions
Rearrange middleware for clarity
Better comments.
Remove unused memcached modules
Merge pull request #133 from airbnb/examples

Adding example of how to set up sessions
Added `middleware` and `config` examples; reorganized

Squashed the following commits:
Demonstrate how to access session data in view.

Adding example using `config` module

Renamed examples to indicate order of progression

Incorporating 01_config's changes into 02_sessions

Actually use `config.server.port`

Adding `middleware` example.

Better way of using middleware for `sessions` example.

Remove `runtime.json` file
Merge pull request #134 from airbnb/examples

Added `middleware` and `config` examples; reorganized
Better debugging of errors in controllers

Don't catch and obscure errors in controllers while building routes. No
reason to hide them at build time just to let them blow up at runtime.
Merge pull request #135 from airbnb/dont-obscure-controller-errors

Better debugging of errors in controllers
Release 0.5.0-alpha05
Refactor `syncer` into mixin for `BaseCollection`, `BaseModel`

This will make it easier to extend the functionality of `BaseModel` and
`BaseCollection`, and to do things like access properties of the `app`
in the various methods.
Merge pull request #138 from airbnb/syncer-mixin

Refactor `syncer` into mixin for `BaseCollection`, `BaseModel`
Separate coverage script from test script
Pass `apiPath` to client-side, so API calls go to right place

Now, simply passing `apiPath` option to `rendr.createServer()` is all it
takes to for models and collections to fetch API calls from the correct
path. Before, setting `apiPath` would set up the middleware at the
correct path, but it wouldn't force models and collections from fetching
from said path.
Fixing tests.
Merge pull request #139 from airbnb/api-path-in-model

Pass `apiPath` to client-side, so API calls go to right place
Release 0.5.0-alpha06