Unit test and fixed bug

[kketernality]

This pull request contains the following updates:

Unit Test

1. Implemented unit test using Catch2 [1] and ported suitable tests from the original Python repository [2]. The unit test files locate in the test folder as before.
2. Updated CMakeLists.txt and README.md to provide instruction of building and running unit test.

Fixed Bugs

• [v] The example from Readme gave the wrong result. The cause is that the full_process is default on and will strip the tailing exclamation mark. It was fixed by altering the default value of full_process to false.

ReadmeExample
FAILED:
      REQUIRE( 97 == fuzz::ratio("this is a test", "this is a test!") );
EXPANSION:
      97 == 100 

• [v] Comparison of two empty strings should give 100% similarity as in the original Python implementation. Fixed by adding additional logic in ratio() and partial_ratio().

RatioTest
      testEmptyStringsScore100
FAILED:
      REQUIRE( 100 == fuzz::ratio("", "") )
EXPANSION:
      100 == 0

• [v] The partial_ratio() of two identical string is 0% similarity which should be 100% undoubtedly. The detailed description is in the fuzzywuzzy.cpp. This was fixed by a temporary solution to compare if two strings is identical or not.

RatioTest
      testPartialRatio
FAILED:
      REQUIRE( 100 == fuzz::partial_ratio("new york mets", "new york mets") )
EXPANSION:
      100 == 0

[tmplt]

Thanks for taking the time to port unit tests over! I'll see about going over the commits the coming week.

[kketernality]

Just let me know if there is anything goes wrong or needs to be updated. ^_^

[kketernality]

I'm not partial to adding a ~17kloc library header. Could you source catch.hpp from a submodule instead?

Okay, I think make it as an installed package or something likewise is more proper. Will be added in the next commit.

[kketernality]

@tmplt

I had updated the required change. Please review the code changes in this new commit.