MySQL connection dsn, charset support

 - added charset support for MySQL dsn string
 - added charset parameter to the phinx configuration
 - updated configuration documentation
Fixes #134. Merge branch 'charset' of https://github.com/szachara/phinx into szachara-charset
fixes PR #193. remove trailing spaces.
updating to 0.3.1
Merge branch '0.3.x-dev'