added WebHistory and WebHistoryItem class, added getCopyBackForwardList, goBackOrForward, canGoBackOrForward and goTo methods for InAppWebView and InAppBrowser, updated docs

fixed onLoadResource, added InAppBrowser.addJavaScriptHandler() and InAppBrowser.removeJavaScriptHandler() methods, v0.3.0

v0.2.1, fixed InAppBrowser.injectScriptCode() method when there is not a return value, added InAppBrowser.onConsoleMessage() method to manage console messages #5

added initial support of SFSafariViewController for iOS, updated ChromeCustomTabs for android, added initial version of _ChannelManager dart class