Added bokeh.report_bug function. Refactored print_versions function a little bit.
Made print_version more clean and simple.
Renamed function and added issue preview.
Refactored to be an interactive function.
Docstrings updated, made the function more generic. Now the function opens the web browser in the issue webpage.
Now the function is able to add comments to already opened issues.
Fixed one line.
Fixed test_print.
Merge pull request #641 from damianavila/reportbug

bokeh.report_bug function