Add note in Posts docs about stripping <p> tags from excerpt.

Fixes #1926. Merges #1933.
Update history to reflect merge of #1933.

[ci skip]
Branding, baby.

Many thanks to http://patorjk.com/software/taag/ for doing the
ASCII art. :smiley:
Merge pull request #1936 from jekyll/branding
Update history to reflect merge of #1936 [ci skip]
Add docs about the 'new' restriction on excludes.
Merge pull request #1938 from jekyll/excludes-relative-to-site-source-docs
Update history to reflect merge of #1938
Add link to contributors in README.

Linkify "awesome contributors" in the README, as in the footer of the [Jekyll home page](http://jekyllrb.com/).
Merge pull request #1940 from robatron/patch-1
Update history to reflect merge of #1940
Add 1.4.3 release post by @BenBalter for master branch.
Update History.markdown with 1.4.3 release.
Require Liquid 2.5.5 <= x < 2.6
update dat gemspec
Update history to reflect merge of #1943 [ci skip]
Forgot #1943 in the line, whoopsie
Update history to reflect merge of #1949 [ci skip]
Make doc menus more reusable
Merge pull request #1947 from jekyll/1-4-3-release-info