Minor improvements, shorten + coding style

[EVODelavega]

Commit messages say it all really:

• Rename snake_cased variables to the preferred camelCase style
• Remove redundant variables, use in-place reassignments
• replace first loop with range + initialise column[0] outside of loop instead of reassigning
• simplified the min implementation (possible because it's not using varargs)
• added a couple of comments for clarification
• added test cases for empty strings
• exported function docs should start with the function name (for godoc)