Add Instructions to Install R and ggplot2

Closes #253
Add New Integration Tests to run_tests.py

Tests added in commit 9f94386d5768a28c6a80b60eec2762567c1cc025
Fix Voice-Pair Bug; Add a Test for It; Change '[all]' to 'all'

Closes #265.

Changes '[all]' and '[all pairs]' to 'all' and 'all pairs' in the
WorkflowManager. So far only for intervals experiment and settings(); next
commit will do this for interval n-grams too.
Change Interval N-Grams to Use 'all' and 'all pairs'

As promised in commit fdb809dd337d88e35d698a64e32a4a9253a7c3