JSON serialisation

Changes:

• Added serialisation to JSON;
• Minor updates and performance optimisations.

Interface enhancement

• csvplus.File renamed to csvplus.Reader;
• Added constructors to create csvplus.Reader from io.Reader and io.ReadCloser;
• Name field removed from DataSourceError, as the input is no longer guaranteed to have a name;
• Minor changes to comments;
• Line numbering now starts from 1 instead of 0.

Bugfix release

Bug fix: Missing csv header when neither of SelectColumns, ExpectHead…

…er, AssumeHeader is called on csvplus.File object.

First beta release.

Minor updates and bug fixes.

First alpha

v0.1.0

Documentation update.