Lint fix: NewApi

Encryptor#init already has a version check, so we can safely wrap the
whole method as @TargetApi(HONEYCOMB)

OAuthWebviewHelper.BaseRinishAuthFlowTask#onPostExecute was using
String.isEmpty, which was added in API 9, but the library project is
currently set to build with API 8. This was replaced with a call to
TextUtils.isEmpty(CharSequence)
Lint: DefaultLocale

Replaced calls to String.toLowerCase() with
String.toLowerCase(Locale.US). Locale.US is guaranteed by Java to be
installed, and can be used to downcase URLs expressed as
Strings.
Lint: ContentDescription

The login header "reload" ImageView could use a contentDescription.
Merge pull request #439 from jasonschroeder/Lint-NewApi

Lint fix: NewApi
Merge pull request #441 from jasonschroeder/Lint-ContentDescription

Lint: ContentDescription
Merge pull request #440 from jasonschroeder/Lint-DefaultLocale

Lint: DefaultLocale