Added a .gitattributes file

This will allow checkouts of the SolveSpace source tree on Unix and Windows
to use the system's native line endings (i.e. LF vs. CRLF), while keeping
Unix line endings in the repository.

Created using the template at

	https://help.github.com/articles/dealing-with-line-endings

.gitattributes

@@ -0,0 +1,22 @@
+# .gitattributes for SolveSpace
+
+# Set default behaviour, in case users don't have core.autocrlf set.
+* text=auto
+
+# Explicitly declare text files we want to always be normalized and converted
+# to native line endings on checkout.
+*.cpp text
+*.h   text
+*.txt text
+
+# Declare files that will always have CRLF line endings on checkout.
+*.sln text eol=crlf
+
+# Denote all files that are truly binary and should not be modified.
+*.gz  binary
+*.ico binary
+*.jpg binary
+*.lib binary
+*.png binary
+
+# end .gitattributes