Pyodbc

Fix decoding of Cursor.description column names. Fixes 190 - The issue was a column alias with an i with acute which caused an error. pyodbc now (1) uses the Unicode version of SQLDescribeColumn and (2) uses the configured SQL_C_WCHAR encoding. I've added SQL Server test decode_meta for this.

When a connection is used in a `with` clause (as a context manager), the connection has always been committed if successful. However, when an exception is raised it now issues a specific rollback. In the past neither was performed if an exception was raised.

Important fixes for reading decimal/numeric columns, gettypeinfo, an error when reading an empty string.

This is a doc-only update to replace 4.0.0 which I removed from PyPI (pip). This should be 100% compatible with 4.0.0.

I was attempting to replace the source tarball for 4.0.0 but that is apparently not allowed. It would have been nice to know that before it let me delete it ;)

You should upgrade to 4.0.2, however, for some important bug fixes.

Unicode handling has been rewritten for correctness. Make _sure_ you read the [Unicode documentation](https://github.com/mkleehammer/pyodbc/wiki/Unicode) if you have any issues.

**MySQL and PostgreSQL users**: You will probably need to add a couple of lines of configuration. See the [Unicode documentation](https://github.com/mkleehammer/pyodbc/wiki/Unicode)!

**WARNING:** The source code for this version is not available on PyPI. Please upgrade to 4.0.2.