Updated the description and using statements in eclipse.txt
Switch to use the plaintext formatting for Apache License

It's very clear that the site had copied over the HTML version of the
Apache License.

See [lines 122 to
142](https://github.com/github/choosealicense.com/blob/4e2fd06748ba8cc61c13b604b5bd947242bcbd63/licenses/apache.txt#L122)
as an example where the unordered list bullets not copied in along with
the rest of the text, throwing off the formatting and bunching together
text.

Since the site is displaying the plaintext version of the license, it
makes more sense to use the nicely formatted [plaintext version provided
by Apache](http://www.apache.org/licenses/LICENSE-2.0.txt).
Change braces to match the rest of the site
Merge pull request #99 from IQAndreas/fix-apache-formatting

Switch to use the plaintext formatting for Apache License
Only include link to source if one has been provided

Not all licenses have provided a `source` property, so this check just
prevent an empty `href` in such cases.
Add license sources where missing
Merge pull request #101 from IQAndreas/fix-missing-sources

Add license sources where missing
Use the plaintext formatting of the Artistic License 2.0

Another case where the license was copied from HTML, but had a nicely
formatted plaintext version (this is the last one, I promise).

This time the source was taken from
<http://www.perlfoundation.org/attachment/legal/artistic-2_0.txt>
fix 'using' display in sidebar
remove garbage 'using' link
add HTML::Proofer
tweaks to make html-proofing pass
run html-proofing as part of travis build
make testing instructions match travis build steps
build gh-pages branch on travis
display build status in readme
include list of tools
Merge pull request #105 from github/build-status

Build gh-pages branch
Merge pull request #106 from github/tools

Include list of tools
Merge pull request #102 from github/fix-using

Fix 'using' display in sidebar