Graphql-core

This release implements the Type Validation System (8)
- Implement type validation and unit tests 8
- Implement `assert_object_implements_interface` 8
- Implement missing enum_type tests.
- Removed submodule `libgraphqlparser`, move everything we need into `scripts`.
- Make `generate_ast` work on py3x
- Use **slots** in classes that seem to be instantiated a lot (to save some memory)

Yet again more potentially breaking fixes if you are using the Executor directly.
- Implement the `get_operation_ast` utility.
- Implement a way to get/set the default executor that is used when you call `graphql.core.graphql()` or `graphql.core.execute()`. You can do this by calling `graphql.core.executor.{get,set}_default_executor()`
- Add the option to specify `map_type` in the Executor. This change allows for you to specify what kind of Map you want to store your result data in. The two recommended options are:
- `dict` (the default). Use this when you don't care about result ordering. For example, you don't care that the order in the fields of your response match the order of the fields in your query. For most cases, this is correct and is the fastest option.
- [`collections.OrderedDict`](https://docs.python.org/2/library/collections.html#ordereddict-objects), when you pass something that is an OrderedDict, or a subclass of it, the executor will switch into "strict ordering" mode, which will make it so that the order of the results, match the order they were defined in the query. Concurrent execution will still execute out of order however if you are running a `Query` (but the results will still return in the correct order), you can override this by passing `execute_serially=True` to the executor (which is generally not needed. But exists incase you want to execute serially for whatever reason). Also, mutations will always execute serially.

You can use any other user implemented mapping type as long as it implements the [`MutableMapping`](https://docs.python.org/2/library/collections.html#collections.MutableMapping) abstract base type.
- The executor no longer takes `schema` in it's constructor. Instead pass this as the first argument to `Executor.execute()`.

More fixes and potentially breaking changes as we gradually implement schema type checking.
- The proper version of `gevent` can now be installed by using `pip install graphql-core[gevent]`.
- Require `six` as a dependency, and use it to handle py2/3 compat instead of `graphql.core.compat`.
- Ensure that values for `args` passed to `GraphQLField` are of type `GraphQLArgument`.
- Implement the `schema_printer` utility.
- Ensure that values for `fields` passed to `GraphQLInputType` are `GraphQLInputObjectFields`.
- For `GraphQLEnumType` use an `OrderedDict` to store values so that we can preserve the order of enums passed in. Additionally, when constructing an `GraphQLEnumType` you should use an OrderedDict to pass in your values as well. But this isn't enforced anywhere, but may raise a warning soon.
- Introspection's object types/enums should be using OrderedDicts for their fields/values, that way the order in the schema printer is going to be consistent.
- Switch argument ordering for `core.utils.value_from_ast` to match reference implementation.
- Allow `GraphQLInputObjectType` to take a callable as a `field` argument.
- Schema types should be built immediately instead of lazily when `get_type_map()` is called. This should allow us to raise exceptions upon construction of the schema, instead of later, upon first execution.
- Implement `build_ast_schema` utility.
- Split validation rules into individual files.
- The executor will now choose to use an ordered dict implementation when collecting the root fields of query/mutation, rather than an unordered-dict implementation to guarantee the order of execution when being executed serially is the same as it is defined in the query. No order guarantees are given for non-serial execution, as per the spec.
- Instead of using `is_nullish`, use a more Pythonic `is None` check. (thank you faassen)
- Remove `setup.py test` instead, use `tox` for testing.

`graphql-core` v0.1-alpha-1 release.
- Performance and memory optimizations to the visitor, parser, lexer and tokenizer.
- Implement latest upstream RFCs (operation name optional, type condition optional).
- Implement schema parser and schema AST printer.
- Add more tests.

Alpha package release: https://pypi.python.org/pypi/graphql-core/0.1a0