(GEP-178) Geppetto Ruby parser should be able to hande BOM's

Add a factory to create an InputStreamReader that is configured
according to a BOM header found on input.
(GEP-164) Handle dropped support for operator += in 4.0

Add a preference that controls reporting when the deprecated
+= operator is used. The default setting for this preference
is 'warning'. The preference is hardcoded to error in when
using version 4.0.
Merge pull request #36 from puppetlabs/issue-178

(GEP-178) Geppetto Ruby parser should be able to hande BOM's
Merge pull request #40 from puppetlabs/issue-164

(GEP-164) Handle dropped support for operator += in 4.0
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(GEP-111) Support chained assignments

Allow AssignmentExpression as RHS in AssignmentExpression and
let validator generate errors when this construct is detected
if the platform in use is version < 4.0