Merge pull request #87 from hugovk/master

Added options for archiving mentions and favorites
I've added the following options to archiver.py:

```
 -m --mentions <file>  archive own mentions instead of timeline into
                       given file name (requires OAuth, max 800 statuses)
 -v --favorites        archive user's favorites instead of timeline
```

This lets me periodically backup all my tweets, favorites and mentions with a batch file something like this:

```
@echo Archiving my tweets
@call twitter-archiver.exe --oauth --save-dir M:\twitter hugovk

@echo.
@echo Archiving my favourites
@call twitter-archiver.exe --oauth --save-dir M:\twitter --favorites hugovk

@echo.
@echo Archiving my mentions
@call twitter-archiver.exe --oauth --save-dir M:\twitter --mentions hugovk-mentions
```