Snowflake example (#16)

* Snowflake example

Snowflake example

* Gears execution for WB with snowflake

RedisGears Write-Behind recipe for snowflake database

examples/snowflake/README.md

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+## Running the recipe
+You can use [this utility](https://github.com/RedisGears/RedisGears/blob/master/recipes/gears.py) to send a RedisGears Write-Behind or Write-Through recipe for execution. For example, run this repository's [example.py recipe](https://github.com/rgsync/examples/snowflake/example.py) and install its dependencies with the following command:
+
+```bash
+python gears.py --host <host> --port <port> --password <password> examples/snowflake/example.py REQUIREMENTS rgsync snowflake-sqlalchemy
+```

examples/snowflake/example.py

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+from rgsync import RGWriteBehind, RGWriteThrough
+from rgsync.Connectors import SnowflakeSqlConnector, SnowflakeSqlConnection
+
+'''
+Create Snowflake connection object
+The connection object will be translated to snowflake://<user>:<password>@<account>/<db>
+'''
+connection = SnowflakeSqlConnection('<user>', '<password>', '<account>', '<db>')
+
+'''
+Create Snowflake person1 connector
+persons - Snowflake table to put the data
+id - primary key
+'''
+personsConnector = SnowflakeSqlConnector(connection, 'person1', 'id')
+
+personsMappings = {
+	'first_name':'first',
+	'last_name':'last',
+	'age':'age'
+}
+
+RGWriteBehind(GB,  keysPrefix='person', mappings=personsMappings, connector=personsConnector, name='PersonsWriteBehind',  version='99.99.99')
+
+RGWriteThrough(GB, keysPrefix='__',     mappings=personsMappings, connector=personsConnector, name='PersonsWriteThrough', version='99.99.99')
+
+'''
+Create Snowflake car connector
+car - Snowflake table to put the data
+license - primary key
+'''
+carsConnector = SnowflakeSqlConnector(connection, 'car', 'license')
+
+carsMappings = {
+	'license':'license',
+	'color':'color'
+}
+
+RGWriteBehind(GB, keysPrefix='car', mappings=carsMappings, connector=carsConnector, name='CarsWriteBehind', version='99.99.99')