Enhancements including help text, enforcing lynx to be present, and proper install of R15B03-1

[neowulf]

• Extracted list_available_erl_versions method.
• Migrating egrep to grep -P. See [http://stackoverflow.com/a/7017787/1216965]
  • egrep didn't work on Mac OS X. Hence, this change.
• Refactor ~/.evm to $EVM_HOME
• Installation of evm scripts will fail if lynx is not found,
• Adding help text which will describe general usage besides additional information such as
  • EVM Home
  • Default Version
  • Versions Cached For Usage
• R15B03-1 gets installed as R15B03 which evm is not able to use / install / default, etc.