Project dependencies have API risk issues

[PyDeps]

Hi, In Deep-Learning-Papers-Reading-Roadmap, inappropriate dependency versioning constraints can cause risks.

Below are the dependencies and version constraints that the project is using

mistune>=0.7.2
beautifulsoup4>=4.4.1
six>=1.10.0

The version constraint == will introduce the risk of dependency conflicts because the scope of dependencies is too strict.
The version constraint No Upper Bound and * will introduce the risk of the missing API Error because the latest version of the dependencies may remove some APIs.

After further analysis, in this project,
The version constraint of dependency mistune can be changed to >=0.1.0,<=0.8.4.

The above modification suggestions can reduce the dependency conflicts as much as possible,
and introduce the latest version as much as possible without calling Error in the projects.

The invocation of the current project includes all the following methods.

The calling methods from the mistune

mistune.markdown

The calling methods from the all methods

point.text.split
clean_text
shorten_title
link.endswith
BeautifulSoup.BeautifulSoup
m2.group
time.sleep
point.find
requests.get
f.close
print
replacements.items
clean_pdf_link
get_extension
m1.group
open
f.write
readme_soup.find_all
mistune.markdown
parser.add_argument
link.replace
print_title
len
os.path.join
join
download_pdf
os.path.exists
reload
os.path.splitext
failures.append
readme.read
os.makedirs
re.search
parser.parse_args
shutil.rmtree
text.replace
argparse.ArgumentParser
sys.setdefaultencoding

@ahmaurya
Could please help me check this issue?
May I pull a request to fix it?
Thank you very much.