Update IsRemoteReachable documentation and trim end of hostname of any slashes

[PlasmaEye]

Changes Proposed in this pull request:

• Remove the "(no http:// or www.)" in the description of IsRemoteReachable as the method is already doing that.
• Trim the end of the host name in IsRemoteReachable of any slashes as the method fails if they are there

This fixes/implements:

• [x] Improvement

Which plugin does this impact:

• [x] Connectivity

[jamesmontemagno]

Looks like you have a build failure here on windows: https://ci.appveyor.com/project/JamesMontemagno/xamarin-plugins/build/2.0.0.143

can you take a look.