v0.4.3

New:

• [Experimental] GraphQL parser/visitor now supports experimental type definition language.
• [Experimental] GraphQL parser now accepts subscription as an operation kind keyword.

Fixes:

• Type definition will no longer allow the use of invalid Name for type, field, and argument names. #145
• Improved error messages for syntax errors relating to numbers.
• No longer modify field definition objects provided to type definitions. #132
• Sundry minor documentation, typo and test improvements.