fix incorrect field name of pkg object

I think that name field does not exist in object pkg. It must be package
Add session_info function
Move package doc template into own function
Don't list add_* in help
More git helpers
Use travis generates full shield md.
Closes #546
Merge pull request #526 from wch/print-sessioninfo

Add session_info function
Merge pull request #514 from adrtod/patch-3

fix incorrect field name of pkg object
Rewrite session_info()
Implement use_data(). Closes #542
Fix think-o spotted by @yihui
Improved shim_help implementation.
Update docs
shim_help not exported
Fix failing test
Uncomment important use_travis code
Implement use_data_raw().
Closes #541
Add rstudio version to session_info
Deprecate username in install_github
Remove deprecated install_github args