Step button.
Merge pull request #9 from jjhall89/guibutton

Guibutton
Implement DataDisplay and SymbolTableNotifier

Currently DataDisplay works only for newly inserted symbol.

SymbolTableNotifier is an observable and DataDisplay is a corresponding
observer. cf. Observer Pattern. This observeable needs to register
DataDisplay before it starts inserting symbols. See Driver (main()) in
DataDisplay for usage.
Merge branch 'master' of github.com:citrin2013/citrin

Conflicts:
	SymbolTableNotifier.java
update
Run to breakpoint. Stop run.
Merge pull request #10 from jjhall89/run

Run to breakpoint. Stop run.
Updated gui panel

Line numbers, a small hack to try to get line numbers to update
immediately, step.gif
DataDisplay has list of tables now

Each scope should have a different table.
Merge branch 'master' of github.com:citrin2013/citrin
Implement DataDisplay add new scope
Minor bug fixes in interpreter
Removed an unnecessary message
DataDisplay update
Fixed a logic bug involving single line if/while statements
Symbol table now receives messages and update when variable is updated

I added a new function "updatedVar" to symbolTableNotifier.  I didn't
want to add the overhead of finding the var by name again, by using
assignVar. Might not be the best way to do it?
Fixed bug with declaring global vars

Added a new function to symbol table: clear(). I'm using it to clear the
table after a run.
Undo redo functionality added.
Merge pull request #17 from jjhall89/undoRedo

Undo redo functionality added.
Added arrays v0.1

Added array functionality, I've done minimal testing.