Changed the titles of the Volumes to match the Jeff's titles
Merge branch 'develop' into titles
Merge pull request #666 from AZaitzeff/titles

Titles
Revised the cython lab, pages 1,3, & 4. Mainly fixing typos, and smoothing out the presentation.
Removed erroneous section numbers from Volume 4.
Added a separate volume for labs no longer included in Volumes 1 - 4.
Added extra labs to the Travis build.
Merge pull request #670 from insertinterestingnamehere/sections

Removed erroneous section numbers from Volume 4.
First version of single pixel lab
Added B-trees lab to extra labs volume.
Fixed typo in travis build file.
Moving forward
Merge pull request #673 from insertinterestingnamehere/extra_labs

Orphaned labs
Changed travis build so that a failed assertion of the existence of a
Volume's pdf file results in a test failure.
Add assertion of existence of pdf for extra labs to Travis build.
Merge pull request #676 from insertinterestingnamehere/travis

Travis
Further revisions to the language in the second half of the Cython lab.
Merge branch 'develop' into cython_revisions

Merge branch 'develop' into cython_revisions
Merge pull request #678 from joshualy/cython_revisions

Cython revisions
Finished up the lab