fix --todos command line parameter

Although the help mentions a --todos command line parameter, specifying this
parameter yields an error. This change fixes the issue.
fix todo loading error

Since the error code return check was added to check the result of
yajl_parse we see an error being reported everytime we load a file
containing todos.
The reason is a wrong buffer size (greater than the actual size) being
passed to the yajl_parse function which would then continue reading
uninitialized memory and trying to interpret it.
This change fixes the issue.
Merge branch 'fixTodosCmdArg' of http://github.com/d-e-s-o/clerk into deso-fixTodosCmdArg
Rename variable json <-> todos