Removing underscores from change log.  Also updated the 'Start Canvas' decription to reflect move from Canvas to Sequence.
Merge pull request #376 from mikeapp/change_log_underscores

Change log updates
Change Log additions from issues
Use latest Proofer
Ignore Gemfile lock
Merge pull request #378 from IIIF/changelogs

Change Log additions from issues
Merge pull request #380 from penibelst/upgrade-proofer

Use latest Proofer
No more ][s in html
Merge pull request #383 from IIIF/more_broken_links

No more ][s in html
greps through kramdown warnings for missing links;
editorial tweaks/fixes to make this work;
updates CONTRIBUTING.md to include link syntax requirements;
Closes #379
Merge pull request #384 from IIIF/rspec

greps through kramdown warnings for missing links