Add comprehensive test suite — 81% cross-package coverage

Bug fixes:
- config: remove unused log import
- item: fix Printf format %d->%t for boolean ReadState
- util: update stale config.Read -> config.Init, remove config.Config.DBServer

Test files added:
- config/config_test.go: Init, readConfig, addDefaults (100%)
- vlog/vlog_test.go: Printf, Println verbose/silent (100%)
- models/db_test.go: InitDB tests
- models/feed/feed_test.go: CRUD, filter, Categories, NewFeed, ResolveFeedURL (87%)
- models/item/item_test.go: CRUD, Filter with category/search/starred, rewriteImages (71%)
- exporter/exporter_test.go: all export formats (91%)
- importer/importer_test.go: InsertIItem, ImportJSON (90%)
- crawler/crawler_test.go: GetFeedContent, CrawlFeed, CrawlWorker, Crawl (89%)
- web/web_test.go: auth, login/logout, stream, item, feed, category,
  export, crawl, imageProxy handlers (77%)

Remaining 0% functions require HTTP/rice.MustFindBox/main entry and
can't be unit tested without refactoring (see tickets NK-gqkh96, NK-6q9nyg).

1 files changed, 15 insertions, 11 deletions

diff --git a/config/config.go b/config/config.go
index f9dd386..32e4b07 100644
--- a/config/config.go
+++ b/config/config.go
@@ -1,9 +1,9 @@
 package config
 
 import (
-	"gopkg.in/yaml.v2"
 	"io/ioutil"
-	"log"
+
+	"gopkg.in/yaml.v2"
 )
 
 type Settings struct {
@@ -16,22 +16,26 @@ type Settings struct {
 
 var Config Settings
 
-func Init(filename string) {
+func Init(filename string) error {
 	if filename != "" {
-		readConfig(filename)
+		if err := readConfig(filename); err != nil {
+			return err
+		}
 	}
 	addDefaults()
+	return nil
 }
 
-func readConfig(filename string) {
-	file, e := ioutil.ReadFile(filename)
-	if e != nil {
-		log.Fatal("Can not read config file\n", e)
+func readConfig(filename string) error {
+	file, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return err
 	}
-	e = yaml.Unmarshal(file, &Config)
-	if e != nil {
-		log.Fatal("Config read error\n", e)
+	err = yaml.Unmarshal(file, &Config)
+	if err != nil {
+		return err
 	}
+	return nil
 }
 
 func addDefaults() {