Merge pull request #1 from envis10n/dev

Add min to traversal options.

Add some more methods for graph handling:

Add createGraph() method.
Add listGraphs() method.
Add method for obtaining vertex collections from a graph.

Last change. Use DocumentData<T> for Graph methods

Change return signature to be ArangoCursor<T>.

ArangoCursor does not automatically retrieve Document objects.

Add Edge and EdgeCollection to mod.ts

Clean up collection.ts

Update axiod to 0.24

Add findOne method to collection.

  - findOne is basically an alias for `(await find(filter))[0]`

Re-organize module layout.

Move arango class to its own file.
Change mod.ts to simply re-export.

Update README.

Add JSDoc comments.
Modfiy visibility of some properties.
Remove unused interfaces.