change links from .ly to .com

[nicolaskruchten]

This will likely require PRs in graphing-library-docs, py-docs and r-docs

[jdamiba]

addressed by plotly/graphing-library-docs#43, plotly/plotly.py#2312, and plotly/plotly.r-docs#45

[nicolaskruchten]

Looks good! Likely introduces a bit of breakage but we can fix those as they come up :)