Declare dependencies explicitly

[dmikurube]

As a library (not a plugin), it should have exact accurate dependencies. With this change, <dependencies> in its POM file would be like below :

  <dependencies>
    <dependency>
      <groupId>org.embulk</groupId>
      <artifactId>embulk-util-timestamp</artifactId>
      <version>0.2.0</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-annotations</artifactId>
      <version>2.6.7</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-core</artifactId>
      <version>2.6.7</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
      <version>2.6.7</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.msgpack</groupId>
      <artifactId>msgpack-core</artifactId>
      <version>0.8.11</version>
      <scope>compile</scope>
    </dependency>
  </dependencies>

[dmikurube]

In builds of example plugins there (embulk-input-example and else), conflicted dependencies are marked as [IGNORE IT].

https://github.com/embulk/embulk-base-restclient/runs/917908045

============================================ WARNING ============================================

> Configure project :embulk-input-example
Following "runtime" dependencies are included also in "compileOnly" dependencies.

  ([IGNORE IT] "org.msgpack:msgpack-core:0.8.11")
  ([IGNORE IT] "com.fasterxml.jackson.core:jackson-databind:2.6.7")
  ([IGNORE IT] "com.fasterxml.jackson.core:jackson-annotations:2.6.7")
  ([IGNORE IT] "com.fasterxml.jackson.core:jackson-core:2.6.7")

...

[dmikurube]

Thanks!