Don't catch exception threw by callback
Pass exception correctly
Style fix before merge

Closes #71
Adds explicit children mode that puts children element into distinct property ('$$' by default).
Adds corresponding tests cases.
Docs updated.
Adds .npmignore rules to exclude ignore src, tests and build script from NPM packages.
Keep current version.
Restore indent for options object
Skips empty children properties in `explicitChildren` mode.
Tests added.
Docs updated.
Also cleans `charsAsChildren=true` test case to make it more meaningfull.
Revise docs