Removed `--drivermem` as well as cleanup of the help message.

Per review on the [Pull Request 116](https://github.com/apache/spark/pull/116).

* Removed `--drivermem` as an optional argument.
* References to Spark, Spark Context and Spark Shell are capitalized.
* References to port, address, ip and others are not capitalized.
* Options don't have the 'num' qualifier anymore.
* The example was expanded.

[ticket: SPARK-1186] : Enrich the Spark Shell to support additional arguments.
https://spark-project.atlassian.net/browse/SPARK-1186

Author      : bernardo.gomezpalacio@gmail.com