add lesson 44 - string functions
add lesson 45 - string formatting
add lesson 46 - regular expressions
add lesson 47 - json
add lesson 48 - time
add lesson 49 - epoch
add lesson 50 - time formatting/parsing
add lesson 51 - random numbers
add lesson 52 - number parsing
add lesson 53 - url parsing
add lesson 54 - sha1 hashes
add lesson 55 - base64 encoding
add lesson 56 - reading files