Gridmap

With the previous release things could still go wrong if a process died at just the wrong moment when we're trying to get it's status, so I've added some exception handling to take care of that. I've also:
- Added a `--version` option for `gridmap_web`
- Fixed an issue where log files weren't being attached to error reports.
- Changed the wording of some logging messages.

This release mostly features greatly improved reliability of stalled job detection, but also includes some refactoring. Here's the complete list:
- Modified CPU load calculations used to determine if a job is stalled now included all of the children of a process. Before, if a parent process was sleeping and children were doing all the work, the job would get incorrectly detected as stalled and be resubmitted. This was particularly problematic for [SKLL](https://github.com/EducationalTestingService/skll).
- CPU usage and memory histories are now reset when a job is resubmitted. This means error emails will contain more sensible graphs for resubmitted jobs.
- Now raise a `JobException` if we give up on a job instead of ending up in a bad state.
- Renamed `SEND_ERROR_MAILS` environment variable to `SEND_ERROR_MAIL`.
- Removed deprecated `pg_map` function. It was replaced by `grid_map` in 0.9.2
- Removed `runner` module from generated API documentation, because no one should really need to use it directly.
- Renamed `Job.job_id` to `Job.id`
- Added missing `local` option to `grid_map`.
- Added a bunch more unit tests.

Fix typo in `gridmap.runner.get_memory_usage`

Bug-fix release. Changes are:
- `JobMonitor` is now a context manager so that all jobs get killed when an exception occurs.
- All jobs are now killed if a single job encounters an exception.
- Jobs no longer pass back exceptions as strings, where they go totally unnoticed.
- Cleaned up debug output a bit.
- Much prettier tracebacks for job exceptions.

Just a minor bugfix release. Changes are:
- Switched to using official version of [drmaa-python](https://github.com/drmaa-python/drmaa-python), because it is now up-to-date on PyPI.
- Added .gitatttributes file to keep line endings normalized.
- Fixed issue where jobs that exceed resubmission limit would infinitely send error reports.
- We now check to see if the DRMAA C library was imported correctly and switch to local mode if it wasn't, instead of just crashing (19).
- Switch to using psutil for process CPU and memory stats (18).

- Made web front-end for job monitoring a separate script, `gridmap_web`,
since it can be used to talk to any `JobMonitor` instance. (Fixes 14)
- Fixed crash if a stalled job comes back from the dead (15).
- Fixed crash if job's hostname is somehow not in white list and the job
needs to be resubmitted (16).
- Fixed crash from trying to set `matplotlib` back-end multiple times.
- Cleaned up some imports and removed some unused variables.