add tests for exception classes
add tests for exception classes
rebase against correct version of Expression class
Merge branch 'exception-issues' of git@github.com:MurphEngineer/whdl.git into exception-issues

Conflicts:
	src/test/java/org/whdl/frontend/syntaxtree/TestMultipleAssignmentException.java
	src/test/java/org/whdl/frontend/syntaxtree/TestVariableNotAssignedException.java
Merge branch 'master' into exception-issues
This uses code from an updated public upstream
remove static instances from test getters
the modified methods now return a new instance every time they are
called
Merge pull request #64 from MurphEngineer/exception-issues

Added unit tests for exception classes