Correct escaping of \textwidth in image file drop action

Otherwise inserts "extwidth" which doesn't work
Correct numbering of placeholders in image file drop action

Previously was inserting the content of $1 as the image width.
Use version 1.8 of ruby for bundle items

10.7 and 10.8 only include ruby 1.8, so all bundle items have been written to work with that. Optionally supporting ruby 1.9 and 2.0 is problematic as these versions are not fully backwards compatible.

#ignore
Partially revert "Updates to latexmk, texparser."

This (partially) reverts commit a492bd9aceb0bf3b1107e99ab6fcf9648ef9a0b6 and fixes #26.

Presumably during debug someone commented the exit code propagation which broke the automatic closing of the HTML window.

I reverted all changes to the tmCommand, since the original commit was only about updating latexmk.pl (and some tex parser update, which should probably have been factored out into its own commit with corresponding log).

The info.plist had metadata added that should only appear in managed bundles, but this was already reverted (sans the doc type) in ab2f3010.
Fix label completion (⌥⎋)

It now works with empty braces, does proper snippet escaping of inserted text, places caret correctly, etc.
Improvements to "LaTeX Symbol Based on Current Word" ⌘\

Always insert the leading \ if needed. Work in wider variety of places by taking the current line as input instead of just the current word. Fixes #46 and #71.