Implement initial twitterstats module

* Create module skeleton based off of the existing twitter module
  * Strip out unused pieces and try to make it as minimal as possible
 * Implement settings parsing, converting the untyped `screenNames` slice into an slice of strings
 * Implement initial minimal display, showing a table with all usernames and their follower count + # of tweets (using dummy metrics for now)

modules/twitterstats/client.go

@@ -0,0 +1,48 @@
+package twitterstats
+
+import (
+	"log"
+)
+
+type Client struct {
+	apiBase           string
+	consumerKey       string
+	consumerSecret    string
+	accessToken       string
+	accessTokenSecret string
+	screenNames       []string
+}
+
+func NewClient(settings *Settings) *Client {
+	usernames := make([]string, len(settings.screenNames))
+	for i, username := range settings.screenNames {
+		switch username.(type) {
+		default:
+			{
+				log.Fatalf("All `screenName`s in twitterstats config must be of type string")
+			}
+		case string:
+			usernames[i] = username.(string)
+		}
+
+	}
+
+	client := Client{
+		apiBase:           "https://api.twitter.com/1.1/",
+		consumerKey:       settings.consumerKey,
+		consumerSecret:    settings.consumerSecret,
+		accessToken:       settings.accessToken,
+		accessTokenSecret: settings.accessTokenSecret,
+		screenNames:       usernames,
+	}
+
+	return &client
+}
+
+func (client *Client) GetFollowerCounts() []int64 {
+	return []int64{0, 0, 0, 0, 0} // TODO
+}
+
+func (client *Client) GetTweetCounts() []int64 {
+	return []int64{0, 0, 0, 0, 0} // TODO
+}