Assume --skip-tail if the mongod we're connecting to is not a replset.

Print an informative warning, but then just do the import and exit
cleanly.

closes #10
Use YAML.load_file.

closes #7, sorta. I'd like to catch the exception and print something
more friendly than a traceback, but as far as I can tell, doing so
portably across Syck and Psych is more effort than I want to put in
for this issue right now.
Remove unused variable.

The data object is not being used by the code anymore.
Remove rubygems and bundler require.

This means that local development may now require a 'bundle exec' if
you are using Bundler, but that MoSQL will run fine in environments
where the gems are made available through some other means, and
bundler is not available.
Refactor the collections YAML format to be more flexible.
Support both the new and the old schema format
Allow renaming attributes during import.

- Update the README to provide more details about the new configuration format.
- Illustrate the possibility to rename attributes during the import.
- Make it clear that the old configuration format is still supported.
Update the README slightly for grammar and clarity.
Merge branch 'pr/15'
Fix bulk_upsert's fallback case, and add a test.

closes #17.
Rename unit-test directory to match lib/
Support dotted-path notation in column :source specifications.
Add another bit of error-checking when loading collection maps.
Add some documentation on dot-notation in collection maps.
MoSQL 0.2.0
Upsert: Don't rely on catching duplicate key exceptions so heavily.

Our previous upsert logic was:

begin
  INSERT
rescue duplicate_key_value
  UPDATE
end

This works fine, but the default postgresql server config logs the
entire statement on errors, including duplicate keys, which means that
this will rapidly fill the server logs with huge amounts of spew if
MoSQL is running on a collection with a high update volume. Instead,
switch to

if UPDATE updated 0 rows
  begin
   INSERT
  rescue duplicate_key_value
  end
end

This conceivably will have performance impact for INSERT-heavy
workloads (doubling the number of RTTs), but we can worry about that
if and when it becomes an issue for someone.
Switch to MongoClient, and set an op_timeout.

I've seen occasional cases of MoSQL hanging after certain replset
reconfigurations. I suspect there's a mongo-ruby-driver bug I haven't
found yet, but for now, let's just set a long op timeout, and hope
that will kill us if this recurs.