Luigi parameters with defaults from config.

Allow default for a parameter to be specified in a config file.
The config is lazily loaded, so it's not evaluated on parsing
(useful in the case of calling LuigiConfigParser.add_config_path
to add additional configs at runtime).

Also,
* move config into its own module
* a test utility to override configs for testing.
Hive targets have customizable clients

- deprecated old methods
- no deprecate client
Merge pull request #83 from jcrobak/config-defaults

Luigi parameters with defaults from config.
Merge pull request #84 from rathboma/master

Now we pass the hive client to hive targets in the constructor
Classify tasks not found as 'UNKNOWN'

Fixes an exception we've been seeing in certain situations.
Merge pull request #85 from jcrobak/luigi-grep-fix-unknown

Classify tasks not found as 'UNKNOWN'
Support custom scheduler and RPC responder.  Factor out code smell in luigi.server.  Revive remote scheduler test.  Add test-generated files to .gitignore.
Added tox.ini with the smae configuration used by travis

This let developers run the test suite using tox locally before pushing changes
Remove pep8 warnings from luigi.worker module

Still has some warnings, but they are long messages (>80)
Merge pull request #86 from spotify/lallea/custom_scheduler

Support custom scheduler and API responder.
Merge pull request #88 from freyes/upstream

Remove pep8 warnings from luigi.worker module
Merge pull request #87 from freyes/d64b2aa26648bb514c51c0aa76c9627078bde081

Add tox support to run test suite
Utility method to clone tasks. Also set .args and .kwargs on a Task (useful sometimes)
Added customizable scheduler and worker parameters to interface (run, build, and Interface.run) and a customized_run_test
Merge pull request #89 from erikbern/task-args-kwargs

Set .args and .kwargs on a Task (useful sometimes)
Allow multiple comma separated email addresses for error-email in client.cfg
Merge pull request #91 from VisualDNA/support-multiple-emails-for-alerts

Allow multiple comma separated email addresses for error-email in client...
Added task status legend to dependency graph
Fixed graph width in Firefox
Fixed some issues with my previous commit

- .args clashed with HadoopJarJob's .args
- clone didn't work if a Task had global params (why did we add global params? We should remove them)
Merge pull request #92 from VisualDNA/dependency-graph-legend-with-firefox-fixes

Dependency graph legend with firefox fixes