Added the notion of a StreamContext for errors.

In order to accurately report the origin of an error, every level of
translation carries this context, so that errors can be tied to files
and even lines when appropriate.
Added StreamContexts to the parser.

This adds a general SALVEException, which should serve as the basis for
all exceptions that carry a context. Conversion throughout the block
modules to generate the new BlockException type.
Added StreamContext to Action and its subclasses.

Includes the modification of ActionExceptions to carry a context.
Changed Blocks' to_action to handle context passing
Also a minor bugfix on backup action initialization.
Modified commandline runs to print nicer messages.

Instead of throwing the exception, catches it, inspects it, and
prints a pretty error message. Requires some ugly manual handling of
all of the different exception types in case there is a hybrid exception
that inherits from multiple exception types. Looking for a more elegant
solution.

Includes testing that SALVEExceptions are caught, and other exceptions
pass through.
Merge branch 'feature/exceptions/stream-context' into dev
Made test docstrings name util and config tests.

This is a modification to accomodate the way that nose checks docstrings
for test names.
Docstrings for Block tests.

Includes a minor fix for File blocks during path expansion.
Added docstrings for all Action tests.
Added docstrings for commandline tests.
Adds docstrings for all of the reader tests.
Merge branch 'documentation/test-docstrings' into dev
Fixed aggressive backup behavior.

Directory blocks now check the action to see if the action triggers a
full directory backup. So far, there are no defined actions that do so,
although the current code suggests a "remove" action would fit the bill.
Directory backups are not necessary on create and copy because copies
expand into file actions, which trigger their own backups.
File touches no longer trigger backups. This mirrors the Directory
change, but includes "create" in the backup triggering actions.
Updated version in README to 1.0.1