fix wrong links and punctuations

[chentao1596]

First commit: According to my understanding, "upstreams" should be replaced by "backends".

Second commit:

1. line 225 and line 271 used the wrong punctuations
2. i changed other punctuations refer to Document nginx controller configuration tweaks #132

thank you!

[k8s-reviewable]

This change is 

[coveralls]

Coverage remained the same at 43.285% when pulling 7bcdef0 on chentao1596:configuration-correct into fbcedc0 on kubernetes:master.

[aledbf]

/lgtm

[aledbf]

@chentao1596 thanks!