`bs4` is `beautifulsoup4`

[jakirkham]

Replace bs4 with beautifulsoup4 as they are the same and the former is merely an alias.

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This change is 

[jni]

Thanks @jakirkham! Having you contribute here makes me very happy. =)

[jni]

Hmmm though actually the wercker build crashed, and appears to be related... Do we need to pin a version somewhere?

[jni]

Hmmm this is strange. @stefanv might have some insights...

[jakirkham]

Was thinking BeautifulSoup4 4.6.0 was causing the issue, but pinning doesn't seem to help. 😕

ref: https://app.wercker.com/elegant-scipy/elegant-scipy/runs/build/5b1626341af74e00013eb7b7?step=5b16265aa916600001137d74

[stefanv]

I have not been able to debug this issue; lxml is installed, and that same environment works for me locally!

[jni]

Hmm, this is concerning, to say the least! I guess I vote for merging this anyway in that case...!