Outputs a graphviz compatible .dot file that is a graph of the connections of
different types in the target dir. Uses the fork github.com/firegoblin/gographviz
of github.com/awalterschulze/gographviz to handle making the dot file.
The fork adds an interface for GraphableNode and functions upon it to work with
the program.  Uses go/ast and go/parser extensively for parsing the target dir.

brew install graphviz (or visit http://www.graphviz.org/ for other options)

go get github.com/firegoblin/golangTypeGraph
go install github.com/firegoblin/golangTypeGraph

golangTypeGraph github.com/UserName/TargetDir > output.dot
dot -Tpng output.dot > output.png

Struct -> Struct:
	parent
	field
	inherited
Struct -> Interface:
	implments
Interface -> Struct:
	inherited
	field

-depth int
	maximum depth of recursively searching imports (default 1)
-edgeless
	include nodes that have no edges connected to them (default true)
-env string
	environment variable to use instead of GOPATH (default "GOPATH")
-exports
	marks whether only exported nodes are shown
-file string
	file to parse on, relative to $GOPATH/src (default "github.com/firegoblin/golangTypeGraph")
-imax int
	the maximum number of structs implementing an interface before edges are not drawn (default 9)
-json
	include tags for struct fields in print out
-pkg string
	the package that will not have its types prefiexed with package name (default "main")
-test
	whether or not to include test files in the graph

Compiles
Expects dir to be in $GOPATH/src (unless -env is set, then checks in in $<env>/src)
Assumes default golang style import folders
Does not use import . or renaming

Repeat definitions are ignored (temporary workaround for OS specific files)
Error handling added to protect against crashes on unexpected cases

Output file flag
Perform the dot command for conversion to graphics file types through the program
Modify verbosity of nodes

Add connections to functions, partiularly interfaces to functions they're used in
Add tests to allow safer changes.
Print the string to a file instead of piping
Better attributes, especially to ensure a less cluttered layout.
Seperate ast_helper into on package as contains some useful general AST functions.