Implemented full-text search.

You can now use the search bar on the conversation list to find
conversations, messages, and contacts.

src/org/thoughtcrime/securesms/util/Debouncer.java

@@ -0,0 +1,32 @@
+package org.thoughtcrime.securesms.util;
+
+import android.os.Handler;
+
+/**
+ * A class that will throttle the number of runnables executed to be at most once every specified
+ * interval.
+ *
+ * Useful for performing actions in response to rapid user input, such as inputting text, where you
+ * don't necessarily want to perform an action after <em>every</em> input.
+ *
+ * See http://rxmarbles.com/#debounce
+ */
+public class Debouncer {
+
+  private final Handler handler;
+  private final long    threshold;
+
+  /**
+   * @param threshold Only one runnable will be executed via {@link #publish(Runnable)} every
+   *                  {@code threshold} milliseconds.
+   */
+  public Debouncer(long threshold) {
+    this.handler   = new Handler();
+    this.threshold = threshold;
+  }
+
+  public void publish(Runnable runnable) {
+    handler.removeCallbacksAndMessages(null);
+    handler.postDelayed(runnable, threshold);
+  }
+}