Previously with nmap I found it easy to understand the strengths of ciphers noted by the tool (strong, weak...) 

However this has now changed to a rating of A-F.  What does this mean and why did they make that change?

Below is an example of the output of the tool

<pre>
|  TLSv1.2: 
|     ciphers: 
|       TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA (dh 1024) - D
|       TLS_DHE_RSA_WITH_AES_128_CBC_SHA (dh 1024) - A
|       TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 (dh 1024) - A
|       TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 (dh 1024) - A
|       TLS_DHE_RSA_WITH_AES_256_CBC_SHA (dh 1024) - A
|       TLS_DHE_RSA_WITH_AES_256_CBC_SHA256 (dh 1024) - A
|       TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 (dh 1024) - A
|       TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA (dh 1024) - A
|       TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA (dh 1024) - A
|       TLS_DHE_RSA_WITH_SEED_CBC_SHA (dh 1024) - A
|       TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA (secp384r1) - C
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (secp384r1) - A
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 (secp384r1) - A
|       TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (secp384r1) - A
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (secp384r1) - A
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 (secp384r1) - A
|       TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (secp384r1) - A
|       TLS_ECDHE_RSA_WITH_RC4_128_SHA (secp384r1) - A
|       TLS_ECDH_anon_WITH_3DES_EDE_CBC_SHA - F
|       TLS_ECDH_anon_WITH_AES_128_CBC_SHA - F
|       TLS_ECDH_anon_WITH_AES_256_CBC_SHA - F
|       TLS_ECDH_anon_WITH_RC4_128_SHA - F
|       TLS_RSA_WITH_3DES_EDE_CBC_SHA (rsa 4096) - C
|       TLS_RSA_WITH_AES_128_CBC_SHA (rsa 4096) - A
|       TLS_RSA_WITH_AES_128_CBC_SHA256 (rsa 4096) - A
|       TLS_RSA_WITH_AES_128_GCM_SHA256 (rsa 4096) - A
|       TLS_RSA_WITH_AES_256_CBC_SHA (rsa 4096) - A
|       TLS_RSA_WITH_AES_256_CBC_SHA256 (rsa 4096) - A
|       TLS_RSA_WITH_AES_256_GCM_SHA384 (rsa 4096) - A
|       TLS_RSA_WITH_CAMELLIA_128_CBC_SHA (rsa 4096) - A
|       TLS_RSA_WITH_CAMELLIA_256_CBC_SHA (rsa 4096) - A
|       TLS_RSA_WITH_IDEA_CBC_SHA (rsa 4096) - A
|       TLS_RSA_WITH_RC4_128_MD5 (rsa 4096) - A
|       TLS_RSA_WITH_RC4_128_SHA (rsa 4096) - A
|       TLS_RSA_WITH_SEED_CBC_SHA (rsa 4096) - A
</pre>