Software versions are often written as two numbers - major and minor revision - separated by a dot. A version with a larger major revision is always higher than a version with a lower major revision. For example, version 6.1 is higher than version 5.3 because 6 is larger than 5. Within the same major revision, a larger minor revision indicates a higher version. For example, version 2.11 is higher than version 2.5 because 11 is larger than 5.

Write a function called compare_versions that takes two of these version number strings, returning 1 if the second version is higher than the first, -1 if the first is higher, and 0 if they are the same. For example, given 5.3 and 6.1 you would return 1 because 6.1 is a higher version. You may assume that both strings are in this format.