API was refactored (closes CLI/Lib Refactor #393):

• BREAKING CHANGE: LuaTranspiler was removed
• Added a new function transpile, that runs program.emit with custom transformers and collects emitted results
• Added emitTranspiledFiles function, that writes results to disk. Later it would be replaced by Compilation class (New module resolution and Compilation structure #432).
• All public transformation APIs now return ts.Diagnostic[] instead of throwing/logging/exiting (Return ts diagnostics instead of throwing errors from transformer #412 still isn't completely resolved, since for now it just catches TranspileError thrown from transformer).
• All public APIs now are exported from package index file
• Added 3 new high-level API functions - transpileFiles, transpileProject, and transpileVirtualProject
• BREAKING CHANGE: Changed signature of transpileString to receive only a string and options. Old features may be done with transpileVirtualProject.
• BREAKING CHANGE: CompilerOptions aren't case-insensitive anymore. It should be normalized before using from the API.
• BREAKING CHANGE: CLI-related functions aren't exported anymore.

CLI was refactored:

• Internal structure now is more similar to tsc
• Diagnostics are formatted like in tsc now, with a support of pretty reporter
• Since transformation pipeline now returns diagnostics, transpilation errors are reported just like any other diagnostics. Resolves Improve error reporting #368.
• Watch mode now supports reloading of config file
• Running CLI without a project or files now searches for tsconfig.json (like tsc)
• Option names in CLI are case-insensitive now
• Root-level options are deprecated
• BREAKING CHANGE: Boolean options as strings ("true" and "false") are no longer allowed
• BREAKING CHANGE: Unknown options in tstl config object are considered as errors now

Added support for some emit-related flags:

• declaration
• declarationMap
• emitDeclarationOnly
• noEmit
• noEmitOnError (it's not default anymore)