Standardize reading from IO like objects, including StringIO

[jvshahid]

The main objective of this PR is to fix #1888, i.e. handling of StringIO when parsing HTML documents. There are other commits to refactor the JRuby code and remove any duplicate code. The two areas were we had duplicate code were:

1. Determining if the object being parsed was an IO-like or String object. This is already known since the entry points from Ruby is either read_memory or read_io.
2. Determining the encoding of the object. We were doing this in multiple places and had multiple helper methods to find the encoding. Most of that code is now consolidated in ParserContext.java
3. Letting the parser know about the encoding. We were doing this in multiple places. This is now consolidated into one place ParserContext.java.

[codeclimate]

Code Climate has analyzed commit bf2c547 and detected 6 issues on this pull request.

Here's the issue category breakdown:

Category	Count
Duplication	6

The test coverage on the diff in this pull request is 100.0% (80% is the threshold).

This pull request will bring the total coverage in the repository to 93.5%.

View more on Code Climate.

[jvshahid]

FYI, the failures in CI are reproducible on my local dev machine after running the following to change the locale:

export LANG=C.UTF-8
export LANGUAGE=
export LC_CTYPE="C.UTF-8"
export LC_NUMERIC="C.UTF-8"
export LC_TIME="C.UTF-8"
export LC_COLLATE="C.UTF-8"
export LC_MONETARY="C.UTF-8"
export LC_MESSAGES="C.UTF-8"
export LC_PAPER="C.UTF-8"
export LC_NAME="C.UTF-8"
export LC_ADDRESS="C.UTF-8"
export LC_TELEPHONE="C.UTF-8"
export LC_MEASUREMENT="C.UTF-8"
export LC_IDENTIFICATION="C.UTF-8"
export LC_ALL=

Prior to setting those env vars, locale output was:

locale
LANG=en_US.UTF-8
LC_CTYPE=en_US.UTF-8
LC_NUMERIC=en_US.UTF-8
LC_TIME=en_US.UTF-8
LC_COLLATE=en_US.UTF-8
LC_MONETARY=en_US.UTF-8
LC_MESSAGES=en_US.UTF-8
LC_PAPER=en_US.UTF-8
LC_NAME=en_US.UTF-8
LC_ADDRESS=en_US.UTF-8
LC_TELEPHONE=en_US.UTF-8
LC_MEASUREMENT=en_US.UTF-8
LC_IDENTIFICATION=en_US.UTF-8
LC_ALL=

and after:

locale
/usr/bin/locale: Cannot set LC_CTYPE to default locale: No such file or directory
/usr/bin/locale: Cannot set LC_MESSAGES to default locale: No such file or directory
/usr/bin/locale: Cannot set LC_ALL to default locale: No such file or directory
LANG=C.UTF-8
LC_CTYPE=C.UTF-8
LC_NUMERIC=C.UTF-8
LC_TIME=C.UTF-8
LC_COLLATE=C.UTF-8
LC_MONETARY=C.UTF-8
LC_MESSAGES=C.UTF-8
LC_PAPER=C.UTF-8
LC_NAME=C.UTF-8
LC_ADDRESS=C.UTF-8
LC_TELEPHONE=C.UTF-8
LC_MEASUREMENT=C.UTF-8
LC_IDENTIFICATION=C.UTF-8
LC_ALL=

[flavorjones]

@jvshahid This changeset is fabulous. Thank you for doing all this work. Merging and queueing up for v1.11.0.