Added build script
Updated build instruction in README to mention ``./build.sh`` script.
Added CONTRIBUTING doc
Pass `file.encoding`` VM argument to process that executes the worksheet

* Don't use interpolated string in test ``WorksheetEvalTest.unicodeCharactersAreAllowed``
   for keeping compatibility with Scala 2.9.
* Disabled test ``WorksheetEvalTest.unicodeCharactersAreAllowed`` because it fails from
   the command line when executed on MacOSX (I'll re-open ticket #124).
* Pass the ``file.encoding`` to the JVM used to execute the instrumented worksheet source.
   This is necessary for the result output to be in the right encoding.
* Added an ``encoding`` member to the ``DocumentHolder`` to reduce duplication.
Merge pull request #127 from dotta/transient/spring-clean-up

Transient/spring clean up