Crossplane

* Reorganized build logic so now there's a python interface for building/writing config files given a full crossplane payload: `crossplane.builder.build_files`

* Fixed bug where crossplane wouldn't report error messages correctly when the last directive in a config was missing a semicolon.
* Added the `--strict` flag to crossplane parse that should be used if you want to check for unknown directives/spelling errors.
* Added the `--combine` flag to crossplane parse that will take the multiple config files and read them as one combined config by using the include directives.

* Added an `--include-comments` flag to `crossplane parse` so you can now parse inline comments like NGINX directives.
* Added the ability to handle special block directives that contain embedded lua code like the [`content_by_lua_block`](https://github.com/openresty/lua-nginx-module#content_by_lua_block) directive from OpenResty's ngx_http_lua_module .
* Version 0.3.0 was broken due to an ImportError. This version should not have these problems.

* Added ability to build configuration files from JSON payloads.
* NGX_CONF_FLAG directives now accept case-insensitive arguments.

* Added more options to crossplane parse

* Fixed acceptable contexts for the "state" directive