Add D3 visualization and some helper code

The visualization is a bubble chart of consonant frequencies in the
Bhagavad Gita. The site's JavaScript now contains some helper code for
creating bubble charts in the future. It also contains some helper code
for pie charts and bar graphs, both of which were considered and
eventually rejected for this particular visualization.
Expand guide/help

The page now has more helpful instructions on compiling custom PDFs.
Add first draft of devanagari/punctuation
Add first draft of devanagari/numerals
Fix typo in sounds/compound-vowels
Fix default MW app URL to depend on input script

Remove a bug that pushed an SLP1 URL regardless of the input script
specified in the query form. This bug also reran non-SLP1 queries as
SLP1 queries, with predictably bad results.
Update gitignore to ignore PDFs
Update consonant distribution data

I'm not sure of where the initial values came from, but they seem not
to reflect the actual distribution of letters in the text.
Add visualization for Devanagari vowels
Reorder Devanagari lessons

Consonant clusters are more important than vowels!
Add first draft of devanagari/consonant-clusters
Add first draft of devanagari/vedic-devanagari
Fix rendering bug on gathered headings

If the lesson has no <h2> elements, don't append a <ul> element; the
<ul> will act as extra padding on the highlighted link.
Combine dev/punctuation and dev/numerals

Each lesson is too short to stand alone. But together, they form
something more respectable.
Add candrabindu to devanagari/marks
Tweak line-height in ul.letters

<li> has a line height of 1.6em, but ul.letters should use the browser
default to prevent clipped letters.
Rename 'bubbleGraph' to 'bubbleChart'

This conforms to how the chart is usually described.
Add: select Sanscript output when output box is clicked
Fix routing bug in MW

Remove a bug that transliterates the query string to SLP1 on form
queries while treating the SLP1 output as encoded in the original
scheme. For example, searching for 'atha' in HK caused a search for
'aTa' in HK, which is a search for 'awa' in SLP1.
Modify lesson choices for 'Basics'

The unit contains just enough information to start talking about
participles and compounds. A discussion of gender and various
indeclinables can wait until later on.