Fix inline diff bug

[j2gl]

1. Fixes bug of inline diff, and also added some unit tests.
2. Add some documentation

java.lang.ArrayIndexOutOfBoundsException: 1

    at difflib.DiffRowGenerator.copyEqualsLines(DiffRowGenerator.java:418)
    at difflib.DiffRowGenerator.generateDiffRows(DiffRowGenerator.java:387)
    at difflib.DiffRowGenerator.generateDiffRows(DiffRowGenerator.java:281)
    at diffutils.DiffRowGeneratorTest.testGenerator_InlineDiff(DiffRowGeneratorTest.java:34)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at junit.framework.TestCase.runTest(TestCase.java:176)
    at junit.framework.TestCase.runBare(TestCase.java:141)
    at junit.framework.TestResult$1.protect(TestResult.java:122)
    at junit.framework.TestResult.runProtected(TestResult.java:142)
    at junit.framework.TestResult.run(TestResult.java:125)
    at junit.framework.TestCase.run(TestCase.java:129)
    at junit.framework.TestSuite.runTest(TestSuite.java:252)
    at junit.framework.TestSuite.run(TestSuite.java:247)
    at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:86)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:117)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:262)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:84)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

[EQUAL,anything,anything]
[EQUAL,,]
[EQUAL,other,other]
[CHANGE,more lines,some more lines]
[CHANGE,anything ,anything]
[CHANGE, ,]
[EQUAL,other,other]

[bkromhout]

Hi, I'm so sorry I haven't gotten around to looking at this yet. I'm hoping to find some spare time soon. It does look good preliminarily, I'd just like to verify everything myself and check the language a bit. Thanks so much for doing this though!

[bkromhout]

Great job here @j2gl! I'll merge this and then probably touch up the documentation a little bit. I really appreciate this.

[j2gl]

Thanks @bkromhout!

Maybe you can activate the option to report issues in this repo, I'm doing some work with the library, so maybe I'll add more PR.

Thanks for merging.

j2gl

[bkromhout]

Done, thanks!