PubSub system (#346)

* Add websocketpp dependency

* Initial pubsub commit

Renamed selection min and max variables to selectionMin and selectionMax
to bypass windows min/max macros being stupid.

TwitchAccount is now initialized with its User ID. It cannot be changed
after it has been initialized.

* Update openssl folder

* Update installation instructions

* Split up websocketpp dependency to its own code only and openssl.pri

* Add missing include to asio steady_timer

* Update dependencies for linux

src/util/rapidjson-helpers.cpp

@@ -0,0 +1,19 @@
+#include "util/rapidjson-helpers.hpp"
+
+namespace chatterino {
+namespace rj {
+
+void addMember(rapidjson::Value &obj, const char *key, rapidjson::Value &&value,
+               rapidjson::Document::AllocatorType &a)
+{
+    obj.AddMember(rapidjson::Value(key, a).Move(), value, a);
+}
+
+void addMember(rapidjson::Value &obj, const char *key, rapidjson::Value &value,
+               rapidjson::Document::AllocatorType &a)
+{
+    obj.AddMember(rapidjson::Value(key, a).Move(), value.Move(), a);
+}
+
+}  // namespace rj
+}  // namespace chatterino