v3.0 plans

[johnnyreilly]

This is a meta issue (well really an aide memoire) to list the changes planned for ts-loader 3.0. These are technically breaking changes but are unlikely to break anybody

• drop support for typescript < 2.0 (no-one seems to be using it and we can simplify the code)
• remove entryFileIsJs option; it can be inferred from whether the allowJs TypeScript compiler option has been set.
• move to webpack 3.0 for test harness
• drop configFileName support (replaced by configFile)
• add support for a custom formatter for output - drop visual studio format (this can be added back if there's clamour for it and people can supply their own formatters in the interim)
• make loglevel warn by default (stop outputting typescript version number by default)
• fix tsc has "module" default to "es2015"when targetting es2015+, but ts-loader does not
• switch to yarn because of this
• allow controlling whether the output can contain colours