Added escape character support for BigDataFrame.

Fixed escaped characters sent along as seperator to impala.
Merge pull request #46 from mariusvniekerk/master

Added escape character support for BigDataFrame.
fixed connection error in SQLalchemy due to regex in _get_server_version_info not fully capturing version string (e.g. 'cdh5-1.3.0')
Merge pull request #47 from fkaufer/master

connection error in SQLalchemy due to version string regex mismatch