Update build documentation

The description for building the current version (0.1.4) of the library seems to be broken.

```
./gradlew ktnumpyReleaseSharedLibrary  ✔

> Configure project :
Current branch: null

FAILURE: Build failed with an exception.

* What went wrong:
Task 'ktnumpyReleaseSharedLibrary' not found in root project 'kotlin-numpy'.

* Try:
Run gradlew tasks to get a list of available tasks. Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

Deprecated Gradle features were used in this build, making it incompatible with Gradle 7.0.
Use '--warning-mode all' to show the individual deprecation warnings.
See https://docs.gradle.org/6.0.1/userguide/command_line_interface.html#sec:command_line_warnings

BUILD FAILED in 2s
```

I tried the the same command with an old commit and it seemed to work fine.

Here is additional information regarding my system.
```
~/IdeaProjects/kotlin-numpy  master ?7  ./gradlew --version  1 ✘  4s

------------------------------------------------------------
Gradle 6.0.1
------------------------------------------------------------

Build time: 2019-11-18 20:25:01 UTC
Revision: fad121066a68c4701acd362daf4287a7c309a0f5

Kotlin: 1.3.50
Groovy: 2.5.8
Ant: Apache Ant(TM) version 1.10.7 compiled on September 1 2019
JVM: 1.8.0_192 (Oracle Corporation 25.192-b12)
OS: Mac OS X 10.15.4 x86_64

```

Start by locating the build documentation that describes building version 0.1.4 and compare its ktnumpyReleaseSharedLibrary command with the tasks listed by ./gradlew tasks. Check the documented command against the current project and update the instructions so they match an available build task, then verify the command with the repository's Gradle setup.

Written by the indexing model from the issue text.