BUG: Don't add one-sample trajectories

Trajectories with one sample would fail to be displayed and these would
break the rendering of the animation.
BUG: Enclose queries in quotes

Not enclosing some keywords inside quotes would make jQuery error out
when looking for the queried elements.
TST: Add tests for one-sample trajectories
DOC: Add note to the ChangeLog about bugfixes
STY: Remove whitespace
ENH: Add formatSVGLegend to create plot legends
ENH: Use formatSVGLegend in emperor.js

This removes a lot of code that we now can test.
BUG: Fix incorrect generation of SVG files

Fixes #256
TST: Add test_draw.js

This is module is currently only testing that we can format correctly
the SVG file with the labels.
DOC: Add note about the bug fix
BUG: Fix problem with unique/single valued-columns

If a category in the mapping file had a unique/single valued column,
this would automatically be removed regardless of the fact that the user
could have asked to keep the column. Some tests were fixed to reflect
the case they were checking.

Fixes #271
TST: Add three more test cases related to #271
DOC: Add note about the fix of #271
Merge pull request #291 from ElDeveloper/issue-271

BUG: Fix issue #271
Merge pull request #289 from ElDeveloper/animations-issues

BUG: Fix a few bugs with animations
Merge pull request #290 from ElDeveloper/issue-256

BUG: Fixes issue #256 - Incorrect SVG file generation
Fix #287
Adding option --percent_variation_below_one
Fixing failed test
Addressing comments