docs: added logging documentation (#25)

* added documentation on logging levels

* added environment variable for logging

* added logging redirecting docs

docs/logging.md

@@ -0,0 +1,67 @@
+
+Logging is used throughout dgraphpandas using the standard [logging module](https://docs.python.org/3/library/logging.html).
+
+## Command Line
+
+If you are using the command line tool then setting the logging level is as simple as passing an additional parameter.
+
+```sh
+dgraphpandas -v DEBUG
+```
+
+Where the following levels are supported: `DEBUG,INFO,WARNING,ERROR,NOTSET`
+
+### Coloring Logs
+By default these will log to stdout with no color but you can also add coloring by installing the [`coloredlogs`](https://pypi.org/project/coloredlogs/) module 🌈.
+
+```sh
+python -m pip install coloredlogs
+```
+
+### Environment Variables
+
+The logging level can also be set via environment variable:
+
+```sh
+export DGRAPHPANDAS_LOG=DEBUG
+```
+
+## Module
+
+If you are using dgraphpandas in your own script then you can set logging on a more granular level like so:
+
+```py
+import logging
+import dgraphpandas as dpd
+
+logging.basicConfig()
+logging.getLogger('dgraphpandas.rdf').setLevel(logging.DEBUG)
+logging.getLogger('dgraphpandas.types').setLevel(logging.DEBUG)
+logging.getLogger('dgraphpandas.config').setLevel(logging.DEBUG)
+logging.getLogger('dgraphpandas.strategies.horizontal').setLevel(logging.DEBUG)
+logging.getLogger('dgraphpandas.strategies.vertical').setLevel(logging.DEBUG)
+logging.getLogger('dgraphpandas.strategies.vertical_helpers').setLevel(logging.DEBUG)
+logging.getLogger('dgraphpandas.strategies.schema').setLevel(logging.DEBUG)
+logging.getLogger('dgraphpandas.writers.upserts').setLevel(logging.DEBUG)
+logging.getLogger('dgraphpandas.writers.schema').setLevel(logging.DEBUG)
+
+# your logic
+dpd.to_rdf('input.csv', config, 'config_key')
+```
+
+Naturally this means that you can redirect logs to any handler you would like:
+
+```py
+logging_file = 'dgraphpandas.log'
+
+logging.basicConfig()
+rdf_logger = logging.getLogger('dgraphpandas.rdf')
+rdf_logger.setLevel(logging.DEBUG)
+
+# Create and add any Handler
+formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
+file_handler = logging.FileHandler(logging_file)
+file_handler.setFormatter(formatter)
+
+rdf_logger.addHandler(file_handler)
+```

mkdocs.yml

@@ -7,6 +7,7 @@ nav:
   - Getting Started: 'getting_started.md'
   - Horizontal & Vertical Formats: 'horizontal_and_vertical_formats.md'
   - Configuration: 'configuration.md'
+  - Logging: 'logging.md'
   - Schema & Types: 'schema_and_types.md'
   - Working with Larger Files: 'working_with_larger_files.md'
   - Samples: