Use Github URL in source maps
JVM build doesn't need sourcemaps
Fix warnings related to catch all exceptions
Improve scalac options

+ Set options to warn about deprecation, unchecked, and features to include more descriptive warnings
+ Fix warnings received after setting these options
Merge pull request #41 from ramnivas/throwable-warnings

Fix warnings related to catch all exceptions
Merge pull request #42 from ramnivas/scalac-options

Improve scalac options
Merge pull request #34 from japgolly/sourcemaps

Use Github URL in source maps
Allow custom writers to specify ignoring a value

+ Fixes #40
+ Introduces Js.None, since Js.Null has semantics of Javascript null.
  This allows custom writers to return Js.None to specify that the
  value should not be writen to the output.