Add prawn-table gem

Table support in prawn was extracted into its own gem, so it had to be
added to re-enable tables in the PDFs.
Only show flash messages for warning/error cases

I Removed all the notice type flash messages that just tell you that
whatever you just did was successful. I left in the ones that warned the
user about a problem or that they were not allowed to do something, etc.

I also fixed the code that determines the class names for the alerts,
and updated the alert html to conform to bootstrap 3 norms. Also added
some css to put some margin between the navbar and the alert, or between
alert and alert if there was some way for there to be more than one.
Add notes column to batches table
Add notes to BatchReport PDF, refactor and restyle a bit

Use prawn measurement extensions instead of my custom conversion
function. Also remove padding on the outside columns of the table so
that the text in the table will line up with the text from the notes
that is left aligned.
User can add/edit/update notes and title for batches

When a new batch is created the user can give it an optional title and
enter in any notes they would like to have associated with the batch.
Then, at any time while viewing the batch contributions for that batch
a user may click 'Edit Title & Notes' and modify those values as
desired.

The notes are displayed at the bottom of the batch contributions index
view as well as on the bottom of the batch report PDF.

Did a little bit of refactoring of the batches controller.