Move module code into separate files (#70)

- Move module code out of package init files. This is helpful for auto generated API docs (in addition to being cleaner).
- Add several tests to ensure all modules can be created (e.g., see task/tests/test_task.py)
- Update documentation to use NFCorpus examples
- Fix duplication of NFCorpus documents

capreolus/__init__.py

@@ -2,9 +2,9 @@
 import os
 from pathlib import Path
 
-from profane import ConfigOption, Dependency, constants, config_list_to_dict
+from profane import ConfigOption, Dependency, ModuleBase, constants, config_list_to_dict, module_registry
 
-__version__ = "0.2.1"
+__version__ = "0.2.2"
 
 # specify a base package that we should look for modules under (e.g., <BASE>.task)
 # constants must be specified before importing Task (or any other modules!)
@@ -21,16 +21,18 @@
 jnius_config.set_classpath(Anserini.get_fat_jar())
 
 
-# import capreolus.evaluator as evaluator
-# from capreolus.benchmark import Benchmark
-# from capreolus.collection import Collection
-# from capreolus.extractor import Extractor
-# from capreolus.index import Index
-# from capreolus.reranker.base import Reranker
-# from capreolus.searcher import Searcher
-# from capreolus.task.base import Task
-# from capreolus.tokenizer import Tokenizer
-# from capreolus.trainer import Trainer
+# note: order is important to avoid circular imports
+from capreolus.utils.loginit import get_logger
+import capreolus.evaluator as evaluator
+from capreolus.benchmark import Benchmark
+from capreolus.collection import Collection
+from capreolus.index import Index
+from capreolus.searcher import Searcher
+from capreolus.extractor import Extractor
+from capreolus.reranker import Reranker
+from capreolus.tokenizer import Tokenizer
+from capreolus.trainer import Trainer
+from capreolus.task import Task
 
 
 def parse_config_string(s):