Enable no-opt if mount already mounted

Prior to this commit, a `mount()` call would remount if already
mounted.  This commit makes it so that it literally does nothing if
already mounted, unless `remount=True` flag is passed, in which a
mount will result in a remount.  The operation was already idempotent,
but this makes it sort of more safely side-effect free if already
in the mounted state.
Enable parsing /proc/mounts output

This will help us test if a mount point is already mounted, which
helps us no-op if there's no work to be done (because a drive is
already partitioned, formatted, mounted, and ready to go)
Bump minor version number
Merge pull request #58 from elliot42/master

Improve filesystem mount functionality

This PR improves the `mcv.filesystem` mounting functionality:

1. `mount()` now no-ops if already mounted, unless `remount=True`,
  in which case it will remount.  But it's now side-effect-free by default.

2. You can now call `mount_status()` and/or `mounted(mount_point)` to
  test whether a mount is mounted.  This helps no-op work if things are
  already mounted and ready to go.