Display the default image in case the avatar not available

Note that whenever content is written by another author, the existence of an avatar for that author is questionable, so adding another if-else block ensures that instead of the alt, the default image is shown
Merge pull request #72 from icyflame/master

Display the default image in case the avatar not available
Don't load Disqus script on pages that don't require it
- Was loading Disqus in the script.html include even when a shortname wasn't specified
Combine if statements
Fix typo on theme setup page.
Merge pull request #76 from kevinwang/fix-theme-setup-typo

Fix typo on theme setup page.
Add Magnific Popup
- Image links now display in a lightbox
Add Jekyll and Proofer tests
Add Travis badge
Merge pull request #78 from penibelst/travis

Add build and links test
Escape page title
Fix broken links and add missing alt descriptions
Revert "Fix broken links and add missing alt descriptions"

This reverts commit 98b12d04d9f7cb5c480051e298490fd20d9ea7bf.
Revert "Revert "Fix broken links and add missing alt descriptions""

This reverts commit 67d58a77cf76beba58fe9113ce782501f61436b1.
Remove problematic liquid... for now
Change Twitter share to use tags as hashtags.

Changes the twitter link to use tags instead of categories when
creating the hashtags in the link.
Also removes spaces in tags with multiple words.

For example:

post tags           | twitter hashtags
-----------------------------------------
[open source]       | #opensource
[java]              | #java
[open source, java] | #opensource #java
----------------------------------------
Merge pull request #79 from dacamo76/post-tags-as-twitter-hashtags

Change Twitter share to use tags instead of categories as hashtags.
Replace sitemap.xml with official Jekyll Sitemap gem
Update
Remove reference to sitemap.xml template
- Using Jekyll Sitemap gem instead