Remove TypeScript peer dependency [Blocking latest release]

[dsherret]

My pre-release automated scripts caught a bug that I was about to release in 6.13.0 (kind of cool).

The problem is this library is now implementing features that require a peer dependency of the latest TS version (ex. jsx fragments, strict property initialization). I tried to get around this by generating "compiler polyfills", but this doesn't exactly work because I use ts.SyntaxKind literals in the source. Anyway, as I progress this is going to become more and more of a problem.

The solution I see around this is to provide my own declaration file for the TypeScript compiler along with the library. This would only include the relevant information from the compiler.

[dsherret]

Enums like SyntaxKind and ScriptElementKind should be easily accessible like so:

import {SyntaxKind, ScriptElementKind} from "ts-simple-ast";

But typescript compiler node definitions will be within a ts namespace:

import {ts} from "ts-simple-ast";

const compilerEnumDec: ts.EnumDeclaration;

[dsherret]

Done. This will make the library much easier to use and I won't have to bother supporting multiple versions of the compiler.

If you find something missing on ts that you'd like then please let me know...