* That is true, a tag is not a URI. As far as I can tell, tags are any unicode-character except non-alpha numeric characters less than 128. Using URI is a hack because it converts to URL-encoding for us. Since there should be no slashes etc in a tag, then the URI call should be safe.
* If the URI encoding fails, ```InstagramException``` will be thrown by the call to the api endpoint. This gives us some goodness: if instagram extends what is allowed in hashtags, and these are not value URI characters, then the library should already support it.
* Given (1), I'd rather keep this method specific, since it is only meant for encoding the tag, not the full url of the request.