Major rework of codebase

- Get rid of 'core' and move CLI to cmd/gas directory
- Migrate (most) tests to use Ginkgo and testutils framework
- GAS now expects package to reside in $GOPATH
- GAS now can resolve dependencies for better type checking (if package
  on GOPATH)
- Simplified public API

rules/tempfiles.go

@@ -23,12 +23,12 @@ import (
 
 type BadTempFile struct {
 	gas.MetaData
-	args *regexp.Regexp
-	call *regexp.Regexp
+	calls gas.CallList
+	args  *regexp.Regexp
 }
 
 func (t *BadTempFile) Match(n ast.Node, c *gas.Context) (gi *gas.Issue, err error) {
-	if node := gas.MatchCall(n, t.call); node != nil {
+	if node := t.calls.ContainsCallExpr(n, c); node != nil {
 		if arg, e := gas.GetString(node.Args[0]); t.args.MatchString(arg) && e == nil {
 			return gas.NewIssue(c, n, t.What, t.Severity, t.Confidence), nil
 		}
@@ -37,9 +37,12 @@ func (t *BadTempFile) Match(n ast.Node, c *gas.Context) (gi *gas.Issue, err erro
 }
 
 func NewBadTempFile(conf gas.Config) (gas.Rule, []ast.Node) {
+	calls := gas.NewCallList()
+	calls.Add("ioutil", "WriteFile")
+	calls.Add("os", "Create")
 	return &BadTempFile{
-		call: regexp.MustCompile(`ioutil\.WriteFile|os\.Create`),
-		args: regexp.MustCompile(`^/tmp/.*$|^/var/tmp/.*$`),
+		calls: calls,
+		args:  regexp.MustCompile(`^/tmp/.*$|^/var/tmp/.*$`),
 		MetaData: gas.MetaData{
 			Severity:   gas.Medium,
 			Confidence: gas.High,