Update README.md

Make README consistent with the actual file name
Merge pull request #35 from MarkyV/patch-1

Update README.md
Fix a few description typos
Correct 'is' to 'are' in koan description. 

I don't mean to be That Guy, but it's more correct to use 'are', rather than 'is' when discussing a plural subject. 
Merge pull request #36 from blt/patch-1

Correct 'is' to 'are' in koan description.
Touch up some grammar & wording
Bump to 0.4.7 for line number in message
Some slightly less confusing language for lein idiots like me
Merge pull request #38 from paytonrules/master

Some Minor Readme changes
Updates to Clojure 1.5.0 final
Merge pull request #39 from sl4m/clojure-1-5

Updates to Clojure 1.5.0 final
Update deploy script to get lein1 deps and omit GH
Bump koan-engine for bugfix

Thanks to Manas Karekar for reporting.
Updated README
Merge pull request #43 from manaskarekar/cl-koans-readme

Updated README
Clarify equalities a bit
Clarify empty lists & other list operations
Add some nil exposition
Leave out vec nil for now
Clarify keywords, symbols, maps, sets