MySQL connection dsn, charset support

 - added charset support for MySQL dsn string
 - added charset parameter to the phinx configuration
 - updated configuration documentation
Added signed variable to mysql table
removed stray semicolon
corrected testAddStringColumnWithSiqngedEqualsFalse test
restructured tests so expected & actual are the correct way around
use `empty` to check $options['port']

i want use the `port: %%PHINX_DBPORT%%`, but other people maybe like the default port,
so just given a empty port config.
Fix typo in configuration.rst

devlopment -> development
Merge pull request #189 from 3onyc/patch-1

Fix typo in configuration.rst devlopment -> development
Added valid column types list

I always have to go routing through the source code to find this, so thought it would be useful to include in the main documentation.
Minor whitespace cleanup
Merge pull request #190 from coatesap/0.3.x-dev

Added valid column types section
install improvements
fix copyright
Merge branch '0.3.x-dev'
Adds tests for JSON format config files.
Adds support for JSON config files.
Corrects exception message typo.
fixes PR #171.
Fixes #134. Merge branch 'charset' of https://github.com/szachara/phinx into szachara-charset
fixes PR #193. remove trailing spaces.