use "data size:" instead of "Data in InnoDB tables"

prevents unwanted rounding off for GB size data by mysqltuner.pl when
using summary results.
add 10% to innodb_buffer_pool_size to account for DB growth
fix spacing
Merge pull request #440 from pricejn2/434-buffer_pool

Improve innodb_buffer_pool_size calculation and add 10% for future growth