Remove space between caption and table. Add blank line between caption and figure.
Fix bug in preamble. blackline -> blankline.
Issue #15: Add blank lines around equations

Following changes are included:
* Renew environments equation and align to include blanklines between
text and formulas
* set abovedisplayskip, abovedisplayshortskip, belowdisplayskip,
belowdisplayshortskip to 0pt
* Fix existing equations
 * There should be no blankline in .tex file before equation environment
 * There should be a blank line in .tex file after equation environment