Added caching of underscore to camelCase conversion, for improved performance.

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
# HEAD detached from 35fe5e3
# You are currently editing a commit while rebasing branch 'feature-beginTransactio-as-autoClosable' on '35fe5e3'.
#
# Changes to be committed:
#   (use "git reset HEAD^1 <file>..." to unstage)
#
#	modified:   pom.xml
#	modified:   src/main/java/org/sql2o/Connection.java
#	modified:   src/test/java/org/sql2o/Sql2oTest.java
#