Merge pull request #130 from josephwilk/master

Bug: Nested transactions deadlock with MYSQL.
Revert "Support nested transactions with MYSQL."

This reverts commit cdcd605406b8d3cb739ce786986473bf4456c735.
Revert "Revert "Support nested transactions with MYSQL.""

This reverts commit 11f67cca60c03221829ddf83240e67d515feced9.
Merge pull request #131 from josephwilk/master

Fixing Travis build