Add Changelog (#117)

* refs #111: create a part of CHANGELOG for 3.1.0

To generate this list, I used following command for listing up commits:

```sh
$ git log --no-merges --pretty=oneline --abbrev-commit 3.0.1...b3f3117
```

This change contains just a part of changes, I will continue checking
remaining parts by following command:

```sh
$ git log --no-merges --pretty=oneline --abbrev-commit 7325b87...b3f3117
```

* refs #111: added more changelog

we still have changes in this version. I will continue this task
by following command:

```
$ git log --no-merges --pretty=oneline --abbrev-commit 7fb6ff5...b3f3117
```

* refs #111: update CHANGELOG

CHANGELOG.md

@@ -0,0 +1,61 @@
+# Changelog
+
+This is the changelog for SpotBugs. This follows [Keep a Changelog v0.3](http://keepachangelog.com/en/0.3.0/).
+
+## Unreleased
+
+### Added
+
+* Make TypeQualifierResolver recognize JetBrains NotNull annotations ([Patch #248](https://sourceforge.net/p/findbugs/patches/248/))
+* excludePath and includePath in AntTask ([6668a9](https://github.com/spotbugs/spotbugs/commit/6668a9))
+* Cancellation of queueing FindBugsJob in Eclipse plugin ([bceec81](https://github.com/spotbugs/spotbugs/commit/bceec81))
+* Artifact which contains only SpotBugs annotations ([Bug#1341](https://sourceforge.net/p/findbugs/bugs/1341/))
+* Warn if excludeFilter is empty ([4b7e93f](https://github.com/spotbugs/spotbugs/commit/4b7e93f))
+* Partial Java9 support ([FindBugs#105](https://github.com/findbugsproject/findbugs/issues/105))
+* `spotbugs.home` is available like `findbugs.home` ([#33](https://github.com/spotbugs/spotbugs/pull/33))
+
+### Changed
+
+* Support user preferences exported by the Export->Preferences wizard in Eclipse ([01b7df7](https://github.com/spotbugs/spotbugs/commit/01b7df7))
+* No more dependency in annotations on BugRanker and Priorities ([2f9d672](https://github.com/findbugsproject/findbugs/commit/2f9d672), [725be6e](https://github.com/findbugsproject/findbugs/commit/725be6e))
+* Several classes are now not Serializable ([#85](https://github.com/spotbugs/spotbugs/pull/85))
+
+### Deprecated
+
+### Removed
+
+* Java7 Support ([Issue #19](https://github.com/spotbugs/spotbugs/issues/19))
+* WebCloud and other plugins
+* BlueJ Support
+* Artifact which packages not only SpotBugs annotations but also JSR305 annotations
+
+### Fixed
+
+* Typos in description, documentation and so on
+* StackOverflowError in ValueRangeAnalysisFactory ([Bug#1369](https://sourceforge.net/p/findbugs/bugs/1369/))
+* Command line "@" feature ([Bug#1375](https://sourceforge.net/p/findbugs/bugs/1375/))
+* SOAPMessage.getSOAPHeader() can and does return null ([Bug#1368](https://sourceforge.net/p/findbugs/bugs/1368/))
+* False positive in UC_USELESS_OBJECT  ([Bug#1373](https://sourceforge.net/p/findbugs/bugs/1373/))
+* False positive in NP_LOAD_OF_KNOWN_NULL_VALUE  ([Bug#1372](https://sourceforge.net/p/findbugs/bugs/1372/))
+* Missing java.nio.file.Files support in  OS_OPEN_STREAM ([Bugs#1399](https://sourceforge.net/p/findbugs/bugs/1399/)])
+* False negative in GC_UNRELATED_TYPES  ([Bug#1387](https://sourceforge.net/p/findbugs/bugs/1387/))
+* Not reliable BIT_SIGNED_CHECK ([Bug#1408](https://sourceforge.net/p/findbugs/bugs/1408/))
+* Annotation of SIC_INNER_SHOULD_BE_STATIC_ANON ([Bug#1418](https://sourceforge.net/p/findbugs/bugs/1418/))
+* Bug in ClassName.isAnonymous ([dcfb934](https://github.com/findbugsproject/findbugs/commit/dcfb934))
+* long/double arguments handling in BuildStringPassthruGraph ([370808a](https://github.com/findbugsproject/findbugs/commit/370808a))
+* long/double arguments handling in FindSqlInjection ([32a20db](https://github.com/findbugsproject/findbugs/commit/32a20db))
+* getEntryValueForParameter in ValueNumberAnalysis ([fb11839](https://github.com/findbugsproject/findbugs/commit/fb11839))
+* Do not generate non-constant SQL warnings for passthru methods ([Bug#1416](https://sourceforge.net/p/findbugs/bugs/1416/))
+* Too eager "may expose internal representation by storing an externally mutable object" ([Bug#1397](https://sourceforge.net/p/findbugs/bugs/1397/))
+* Do not report WrongMapIterator for EnumMap ([Bug#1422](https://sourceforge.net/p/findbugs/bugs/1422/))
+* Default Case is Missing With Alias Enum Constants ([Bug#1392](https://sourceforge.net/p/findbugs/bugs/1392/))
+* NPE when launched using IBM JDK on Linux ([Bug#1383](https://sourceforge.net/p/findbugs/bugs/1383/))
+* Serializable should be out of target for  RI_REDUNDANT_INTERFACES   ([FindBugs#49](https://github.com/findbugsproject/findbugs/pull/49/files))
+* nonnull annotations database for java.util.concurrent.ForkJoinPool ((fb8a953)[https://github.com/spotbugs/spotbugs/commit/fb8a953])
+* Better handling for JDT illegal signatures([#55](https://github.com/spotbugs/spotbugs/pull/55))
+* StaticCalendarDetector is constantly throwing ClassNotFoundExceptions ([#76](https://github.com/spotbugs/spotbugs/pull/76))
+* ClassFormatException when analyze class with lambda (INVOKEDYNAMIC) ([#60](https://github.com/spotbugs/spotbugs/issues/60))
+
+## FindBugs 3.0.1 or older
+
+Check [changelog at SourceForge](http://findbugs.sourceforge.net/Changes.html).