Fixed call to traceback.format_exc

This function takes an integer limit (on every version of python) and 
never takes the exception instance. Simply calling this w/o any args 
will cause it to format the whole traceback in the storm error.
Merge pull request #56 from justquick/traceback-format-exc-fix

Fixed call to traceback.format_exc
Complete contribuing page
Fix warnings in documentation building
Add comment to cast to tuple
Expose virtualenv --python as yaml option
Minor style changes to contributing
Merge pull request #58 from poros/contributing_page

Complete contribuing page
Comment adjustments
Merge pull request #64 from poros/virtualenv_python_option

Expose virtualenv --python as yaml option
Merge pull request #63 from ecanzonieri/comment_cast_to_tuple

Add comment to cast to tuple
Update changelog
Fixed Issue #66 on tutorial typo
Merge pull request #67 from smoy/smoy_66_fix_tutorial_typo

Fixed Issue #66 on tutorial typo
Fixed logger name for line spout
Merge pull request #69 from smoy/smoy_fix_example_logger

Fixed logger name for line spout
Update CHANGELOG
Minor style fix
Merge pull request #65 from poros/changelog_update

Update changelog
v0.2.3 release