Fix incorrectly incrementing IDs before sending to server. (#1026)

* Fix incorrectly incrementing IDs before sending to server.

* Add TimelineRepositoryTest, fix adding placeholder, fix String#dec()

* Add more TimelineRepository tests, fix bugs

* Add tests for adding statuses from DB.

app/src/test/java/android/text/FakeSpannableString.kt

@@ -0,0 +1,50 @@
+package android.text
+
+// Used for stubbing Android implementation without slow & buggy Robolectric things
+@Suppress("unused")
+class SpannableString(private val text: CharSequence) : Spannable {
+
+    override fun setSpan(what: Any?, start: Int, end: Int, flags: Int) {
+        throw NotImplementedError()
+    }
+
+    override fun <T : Any?> getSpans(start: Int, end: Int, type: Class<T>?): Array<T> {
+        throw NotImplementedError()
+    }
+
+    override fun removeSpan(what: Any?) {
+        throw NotImplementedError()
+    }
+
+    override fun toString(): String {
+        return "FakeSpannableString[text=$text]"
+    }
+
+    override val length: Int
+        get() = text.length
+
+
+    override fun nextSpanTransition(start: Int, limit: Int, type: Class<*>?): Int {
+        throw NotImplementedError()
+    }
+
+    override fun getSpanEnd(tag: Any?): Int {
+        throw NotImplementedError()
+    }
+
+    override fun getSpanFlags(tag: Any?): Int {
+        throw NotImplementedError()
+    }
+
+    override fun get(index: Int): Char {
+        throw NotImplementedError()
+    }
+
+    override fun subSequence(startIndex: Int, endIndex: Int): CharSequence {
+        throw NotImplementedError()
+    }
+
+    override fun getSpanStart(tag: Any?): Int {
+        throw NotImplementedError()
+    }
+}